Marinate the chicken. Add chicken tenderloins, buttermilk, hot sauce, kosher salt, black pepper, garlic powder, and paprika to a large bowl. Mix until the chicken is fully coated. Cover and refrigerate for at least 1 hour, or up to overnight.
Make the dredge. In a shallow bowl or pan, mix flour, cornstarch, kosher salt, black pepper, paprika, garlic powder, onion powder, cayenne pepper, and baking powder.
Dredge the chicken. Remove each chicken tender from the buttermilk marinade and let the excess drip off. Coat heavily in the flour mixture, pressing the dredge into the chicken so it forms a rough, craggy crust. For extra crunch, dip the coated tender back into the buttermilk, then coat again in the flour mixture.
Rest the breaded chicken. Place the dredged chicken tenders on a wire rack for 10 to 15 minutes. This helps the coating stick during frying.
Heat the oil. Add frying oil to a cast iron Dutch oven or heavy-bottomed pot. Heat to 350°F. Do not overfill the pot.
Fry the chicken. Fry the chicken tenders in batches for 4 to 6 minutes, flipping as needed, until golden brown and crispy. The internal temperature should reach 165°F. Transfer fried chicken to a wire rack.
Make the Nashville hot oil. Carefully ladle 1/2 cup of hot frying oil into a heat-safe bowl or saucepan. Stir in cayenne pepper, brown sugar, paprika, garlic powder, chili powder, kosher salt, black pepper, and onion powder. Mix until smooth.
Coat the chicken. Brush or lightly toss the fried chicken tenders with the Nashville hot oil. Do not soak them too heavily or the crust can soften.
Cook the pasta. Boil elbow macaroni in salted water until just al dente. Drain and set aside.
Make the cheese sauce. In a medium saucepan, melt butter over medium heat. Whisk in flour and cook for 1 to 2 minutes. Slowly whisk in whole milk, evaporated milk, and heavy cream until smooth.
Add the cheese. Lower the heat and stir in cheddar, Monterey Jack, and American cheese. Add kosher salt, garlic powder, black pepper, paprika, and mustard powder. Stir until the sauce is smooth and thick.
Combine the mac and cheese. Fold the cooked macaroni into the cheese sauce. The mac should be creamy and thick, not runny. If it gets too thick, add a small splash of milk.
Optional smoke step. For extra backyard flavor, transfer the mac and cheese to a cast iron skillet and smoke at 225°F for 20 to 30 minutes using apple, cherry, pecan, or maple wood.
Prep the cones. Place waffle cones in a cone stand, tall cups, or parchment cone sleeves so they stay upright.
Build the cones. Spoon warm mac and cheese into each waffle cone, filling it about three-quarters full.
Add the chicken. Place one or two Nashville hot chicken tenders on top of each mac-filled cone.
Garnish and serve. Top with sliced pickles, chopped parsley or chives, hot honey, or a drizzle of ranch if desired. Serve immediately while the chicken is crispy and the cone is still crunchy.