Preheat the oven to 350°F. If using a refrigerated or homemade pie crust, spray a 9-inch tart or deep dish pie pan with cooking spray and fit the crust into the pan. Set aside.
Using a fork, pierce the bottom of the pie crust.
On the stovetop in a skillet saute the diced carrot, red pepper and green onions in a couple of tablespoons of olive oil just until translucent. Season lightly with salt and pepper..
Add the ground beef and cook until no pink remains. Drain any excess fat from the pan before adding the rest of the ingredients.
Add to ⅓ cup of chili sauce, ¼ cup of water, Worcestershire sauce, mushroom soup, onion gravy mix, minced garlic, 1 Tbsp parsley, paprika, thyme, and black pepper. Simmer for 2-3 minutes until all of the ingredients are well blended. Stir in the peas. Taste and adjust the seasonings if needed.
Set the filling aside to cool slightly.
Mix 1 Tbsp of finely chopped parsley into the cold leftover mashed or garlic-her bwhipped potatoes.
Pour the filling into the crust. Use the back of a spoon to spread it evenly.
Spread about ⅓ of the whipped potatoes over the filling and sprinkle with a cup of shredded cheddar cheese.
Finish with the remaining whipped potatoes and sprinkle the top with paprika.
Place into the oven and bake for 30 minutes at 350°F.
Increase the oven temperature to 375°F and continue to bake for an additional 15 minutes until the top is golden.
Remove from the oven and allow to rest on the counter for 10 minutes or so before cutting.