1 tbsp. butter
3/4 c. finely diced onion
1 1/2 cloves garlic, minced
1/3 c. plus 2 tsp. each minced celery, carrot, red bell pepper
1 1/2 c. thinly sliced mushrooms
Dash each salt, white pepper and ground thyme
3 tbsp. chopped fresh parsley, divided
6 (5 oz.) flounder fillets
2 tbsp. each grated Parmesan cheese and mayonnaise
3/4 tsp. Dijon style mustard
1 tbsp. lemon juice

In a small non-stick skillet heat butter until bubbly and hot; add onion and garlic and saute briefly. Add celery, carrot, and red pepper. Cover and cook over medium low heat, stirring occasionally, until vegetables are tender, about 5 minutes. Add mushrooms and seasonings stirring to combine. Increase heat to medium high and cook, uncovered, until all moisture has evaporated; stir in half of parsley. Spoon an equal amount of mixture onto center of each fillet and roll fish to enclose; place stuffed fish rolls in a layer, seam side down, in shallow casserole.

Preheat oven to 400 degrees. In small bowl combine cheese, mayonnaise, and mustard; spread mixture evenly over fillets and sprinkle with lemon juice. Bake until fish is lightly browned and flakes easily when tested with a fork, about 20 minutes; sprinkle with remaining parsley. Serve garnished.