Copycat Keto Alice Springs Chicken

Name: Copycat Keto Alice Springs Chicken
Ingredients: 2 tablespoons yellow mustard; 2 tablespoons dijon mustard; 1/2 cup mayonnaise; 2 teaspoons apple cider vinegar; 1 tablespoon Swerve, confectioners; 1/2 teaspoon garlic powder; 1/4 teaspoon paprika; 4 thin chicken breasts, about 1.5 pounds; 1/4 teaspoon salt; 1/4 teaspoon pepper; 1/4 teaspoon onion powder; 8 oz. button mushrooms, sliced; 1 tablespoon butter; 4 slices of bacon, cooked; 1 1/2 cups cheddar cheese, shredded; optional garnish: scallions