Griddle Philly Cheesesteak Stuffed Portobello Mushrooms
Large portobello mushroom caps griddled until tender, spread with creamy A1 steakhouse mayo, and stuffed with finely chopped thin-sliced ribeye, red bell pepper, and onions. Each mushroom is topped with provolone cheese and finished under the broiler until melted and lightly browned. A hearty griddle appetizer or game day recipe packed with classic cheesesteak flavor.
Equipment
- Outdoor flat-top griddle
- 2 sturdy metal griddle spatulas
- Broiler-safe sheet pan or baking dish
- Sharp knife
- Cutting board
- Spoon for removing mushroom gills
- Small mixing bowl
- Pastry brush or silicone brush
- Tongs
Ingredients
For the Portobello Mushrooms:
- 6 large portobello mushroom caps
- 1 tablespoon neutral cooking oil
- 1/2 teaspoon kosher salt
- 1/4 teaspoon freshly ground black pepper
For the Cheesesteak Filling:
- 1 pound thin-sliced or shaved ribeye
- 1 medium yellow onion diced
- 1 medium red bell pepper diced
- 1 tablespoon neutral cooking oil
- 3/4 teaspoon kosher salt divided or to taste
- 1/2 teaspoon freshly ground black pepper
- 1 tablespoon A1 steak sauce
For the A1 Steakhouse Mayo:
- 1/3 cup mayonnaise
- 2 tablespoons A1 steak sauce
- 1/4 teaspoon freshly ground black pepper
For the Cheese:
- 6 slices provolone cheese
- Additional provolone cheese optional for a heavier cheese layer
Instructions
- Preheat the griddle with one side set to medium heat and the other to medium-high heat, approximately 375–400°F.
- Remove the stems from the portobello mushrooms.
- Use a spoon to gently scrape the dark gills from the underside of each mushroom cap. This creates more room for the cheesesteak filling and helps reduce excess dark mushroom liquid.
- Brush both sides of the mushroom caps lightly with neutral oil. Season with kosher salt and black pepper.
- Place the mushrooms rounded-side down on the medium-heat section of the griddle.
- Cook for approximately 4–5 minutes, until the mushrooms begin to soften and develop some browning.
- Flip the mushrooms so the cavity side is against the griddle.
- Continue cooking for another 3–4 minutes, allowing additional moisture to cook out.
- Remove the mushrooms once they are tender but still firm enough to hold the filling. Transfer them cavity-side up to a broiler-safe sheet pan.
- Add approximately 1 tablespoon neutral oil to the medium section of the griddle.
- Add the diced yellow onion and red bell pepper.
- Season lightly with some of the kosher salt and cook for approximately 5–7 minutes, tossing occasionally, until the onion is tender and the red bell pepper has softened and developed some browned edges.
- Move the cooked onions and red peppers to a cooler section of the griddle.
- Spread the thin-sliced ribeye across the hotter section of the griddle in a fairly thin layer.
- Season the ribeye with the remaining kosher salt and black pepper.
- Let the ribeye sear undisturbed for approximately 60–90 seconds.
- Use two metal spatulas to turn, separate, and begin chopping the ribeye.
- Continue cooking for approximately 2–3 minutes, or until the steak is browned and cooked through.
- Bring the cooked onions and red bell peppers back into the ribeye.
- Add 1 tablespoon A1 steak sauce to the steak and vegetables.
- Using both griddle spatulas, chop the cooked ribeye, onions, and red peppers together into smaller pieces. The mixture should be finely chopped enough to fit neatly inside the portobello caps while still keeping recognizable pieces of steak and vegetables.
- Toss the chopped cheesesteak mixture together until the A1 is evenly distributed, then remove it from the heat.
- In a small bowl, combine the mayonnaise, 2 tablespoons A1 steak sauce, and black pepper. Stir until smooth and creamy.
- Spread approximately 1–2 teaspoons of A1 steakhouse mayo inside each cooked portobello cap.
- Divide the chopped ribeye, onion, and red pepper mixture evenly among the six mushroom caps.
- Gently pack the filling into each mushroom so the caps are generously filled without piling the mixture so high that it falls off.
- Place one slice of provolone cheese over each stuffed mushroom. Fold the cheese slightly if necessary so it follows the shape of the mushroom cap.
- Preheat the oven broiler to high.
- Place the sheet pan approximately 5–6 inches below the broiler.
- Broil for approximately 1–3 minutes, watching continuously, until the provolone is completely melted and develops a few lightly browned spots.
- Remove the mushrooms from the oven immediately once the cheese is melted.
- Allow the stuffed mushrooms to rest for approximately 3–5 minutes before serving.
- Serve warm with additional A1 steakhouse mayo on the side if desired.
Notes
RIBEYE:
Thin-sliced or shaved ribeye is the preferred beef for this recipe. The marbling helps the steak remain tender during the quick, high-heat griddle cook. RED BELL PEPPER:
This recipe specifically uses red bell pepper instead of green bell pepper. Red pepper is sweeter and pairs especially well with ribeye, onion, provolone, A1, and portobello mushrooms. CHOP THE FILLING:
This is an important part of the recipe. Do not leave the steak, onions, and peppers in long cheesesteak strips. Once cooked, chop everything together on the griddle so the filling fits neatly inside the mushroom caps and every bite contains steak and vegetables. PORTOBELLO GILLS:
Removing the dark gills is recommended. It creates additional room for the filling and helps reduce excess dark liquid while the mushrooms cook. DO NOT OVERCOOK THE MUSHROOMS:
The portobellos should be tender but still sturdy enough to support the cheesesteak filling. A1 IN THE FILLING:
A small amount of A1 steak sauce is added directly to the chopped steak and vegetables to build savory steakhouse flavor without overwhelming the ribeye. A1 STEAKHOUSE MAYO:
The sauce uses roughly 2 parts mayonnaise to 1 part A1 steak sauce. Use a thin layer inside each mushroom rather than adding so much sauce that the filling becomes slippery. EXTRA SAUCE:
Serve additional A1 mayo on the side for anyone who wants a stronger steak-sauce flavor. PROVOLONE:
Provolone is the preferred cheese for this SG&G version. It melts smoothly and pairs naturally with ribeye and mushrooms. BROILER:
Watch the mushrooms continuously once they go under the broiler. The provolone can go from melted and lightly browned to burned very quickly. NO BROILER METHOD:
Return the stuffed mushrooms to a lower-temperature section of the griddle, top with provolone, and cover with a melting dome for approximately 30–60 seconds, or until the cheese is melted. MAKE AHEAD:
The ribeye, onion, and red pepper filling can be cooked, chopped, cooled, and refrigerated ahead of time. The A1 mayo can also be prepared up to 1 day ahead. ASSEMBLY:
For the best mushroom texture, cook the portobello caps and assemble the finished mushrooms closer to serving time. DOUBLE BATCH:
For 12 mushrooms, double all ingredients. Cook the ribeye in batches so the griddle stays hot enough to sear the meat instead of steaming it. STORAGE:
Refrigerate leftovers promptly in an airtight container and use within approximately 3 days. REHEATING:
Reheat in a 350°F oven, air fryer, or covered griddle until heated through. Add a fresh piece of provolone near the end if the original cheese has dried out. NUTRITION Estimated nutrition per stuffed portobello mushroom: Calories: approximately 430 Protein: approximately 31 g Carbohydrates: approximately 10 g Fat: approximately 31 g Saturated Fat: approximately 12 g Sodium: approximately 850 mg Sugar: approximately 5 g Fiber: approximately 2 g Nutrition is estimated and will vary based on ribeye, mushroom size, provolone, mayonnaise, A1 steak sauce, oil, and portion sizes.
Thin-sliced or shaved ribeye is the preferred beef for this recipe. The marbling helps the steak remain tender during the quick, high-heat griddle cook. RED BELL PEPPER:
This recipe specifically uses red bell pepper instead of green bell pepper. Red pepper is sweeter and pairs especially well with ribeye, onion, provolone, A1, and portobello mushrooms. CHOP THE FILLING:
This is an important part of the recipe. Do not leave the steak, onions, and peppers in long cheesesteak strips. Once cooked, chop everything together on the griddle so the filling fits neatly inside the mushroom caps and every bite contains steak and vegetables. PORTOBELLO GILLS:
Removing the dark gills is recommended. It creates additional room for the filling and helps reduce excess dark liquid while the mushrooms cook. DO NOT OVERCOOK THE MUSHROOMS:
The portobellos should be tender but still sturdy enough to support the cheesesteak filling. A1 IN THE FILLING:
A small amount of A1 steak sauce is added directly to the chopped steak and vegetables to build savory steakhouse flavor without overwhelming the ribeye. A1 STEAKHOUSE MAYO:
The sauce uses roughly 2 parts mayonnaise to 1 part A1 steak sauce. Use a thin layer inside each mushroom rather than adding so much sauce that the filling becomes slippery. EXTRA SAUCE:
Serve additional A1 mayo on the side for anyone who wants a stronger steak-sauce flavor. PROVOLONE:
Provolone is the preferred cheese for this SG&G version. It melts smoothly and pairs naturally with ribeye and mushrooms. BROILER:
Watch the mushrooms continuously once they go under the broiler. The provolone can go from melted and lightly browned to burned very quickly. NO BROILER METHOD:
Return the stuffed mushrooms to a lower-temperature section of the griddle, top with provolone, and cover with a melting dome for approximately 30–60 seconds, or until the cheese is melted. MAKE AHEAD:
The ribeye, onion, and red pepper filling can be cooked, chopped, cooled, and refrigerated ahead of time. The A1 mayo can also be prepared up to 1 day ahead. ASSEMBLY:
For the best mushroom texture, cook the portobello caps and assemble the finished mushrooms closer to serving time. DOUBLE BATCH:
For 12 mushrooms, double all ingredients. Cook the ribeye in batches so the griddle stays hot enough to sear the meat instead of steaming it. STORAGE:
Refrigerate leftovers promptly in an airtight container and use within approximately 3 days. REHEATING:
Reheat in a 350°F oven, air fryer, or covered griddle until heated through. Add a fresh piece of provolone near the end if the original cheese has dried out. NUTRITION Estimated nutrition per stuffed portobello mushroom: Calories: approximately 430 Protein: approximately 31 g Carbohydrates: approximately 10 g Fat: approximately 31 g Saturated Fat: approximately 12 g Sodium: approximately 850 mg Sugar: approximately 5 g Fiber: approximately 2 g Nutrition is estimated and will vary based on ribeye, mushroom size, provolone, mayonnaise, A1 steak sauce, oil, and portion sizes.