Melt butter in ovenproof/stove top safe casserole. Saute celery, carrots and onion until softened, about 10 minutes.
Add mushrooms and cook until browned, approximately 10 minutes.
Add ground beef and cook stirring occasionally until beef is cooked through and no longer pink.
Stir in crushed tomatoes and bring to a boil.
Reduce heat to low, cover, and cook until thickened slightly, about 30 minutes.
Add peas and cook for an additional 5 minutes.
Top with mashed potatoes and bake 30 minutes until hot and bubbly.
Let cool 10 minutes before serving.
Notes
You can easily substitute turkey for the ground beef in this recipe. Either leftover turkey or ground turkey. If using ground turkey, cook first!
As with any of my recipes, calorie counts and nutritional information varies greatly depending on which products you choose to use when cooking this dish.