Pound chicken till uniform thickness, about 1/2 inch. Melt 3 Tbl butter and whisk with egg; dip each piece of chicken in butter, egg mixture then in breading to coat well; set aside.
To make stuffing, combine 4 Tbl butter and chopped onion in microwave safe 10 in pie plate and cook on high about 1-3 minutes till tender. Add broth and cook additional 2-4 min till boiling. Stir in remaining stuffing ingredients (or boxed stuffing mix) till moist. Divide stuffing into 4 mounds and arrange around edge of pie plate; top each with a chicken cutlet leaving center of plate empty. Top with a paper towel and microwave on high about 12 min till done. Let stand 5 minutes before serving.