Combine bread crumbs, 1/2 teaspoon parsley, 1/2 teaspoon salt, paprika, basil, and 1/8 teaspoon pepper in a shallow bowl.
Put 3 tablespoons butter in a microwave-safe bowl. Heat in the microwave until melted, about 30 seconds. Whisk together with egg in a shallow bowl.
Dip each piece of chicken in butter mixture; coat well with breading. Place on a plate.
Combine remaining 4 tablespoons butter and chopped onion in a microwave-safe, 10-inch pie plate. Cook in the microwave on high until tender, 1 to 3 minutes. Add broth and cook in the microwave until boiling, 2 to 4 minutes. Stir in bread cubes, 2 tablespoons parsley, 1/2 teaspoon salt, sage, and 1/4 teaspoon black pepper. Mix stuffing until moist.
Divide stuffing into 4 mounds arranged around the edge of the pie plate. Top each mound with a breaded chicken cutlet, leaving center of plate empty. Cover pie plate with a paper towel.
Cook in the microwave on high until chicken is no longer pink in the center and the juices run clear, about 12 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Let stand 5 minutes before serving.