Heat oven to 400°F and lightly oil a 9x13-inch baking dish.
Whisk honey, Dijon, mayonnaise, lemon juice, and half the garlic powder in a bowl. Set aside.
Pat chicken dry. Season with 3/4 tsp salt, pepper, paprika, and remaining garlic powder.
Warm olive oil in a large skillet over medium-high heat. Sear chicken 2–3 minutes per side until golden.
Move chicken to the baking dish. Brush each piece with a spoonful of the honey-mustard sauce.
Cook bacon in the same skillet until crisp. Transfer to a plate; leave 1 tbsp drippings in the pan.
Add butter to drippings. Sauté mushrooms with a pinch of salt until browned, 4–5 minutes.
Top chicken with mushrooms, bacon, and both cheeses. Drizzle more sauce over the top.
Bake 10–12 minutes, until cheese melts and chicken reaches 165°F. Rest 5 minutes.
Garnish with parsley and serve with remaining sauce on the side.