Preheat oven to 425 degrees. Heat oil in a large frying pan and break in beef, sauteing and breaking up clumps until no longer pink. Remove from pan, leaving drippings behind. Add onion, garlic and thyme and cook until soft about 5 minutes. Add flour and tomato paste and stir to combine.
Add cooked beef, stock, sauces, and about a teaspoon of salt and 1/2 teaspoon of pepper. Bring to a boil, reduce heat and simmer until the sauce thickens a bit, about 5 minutes. Season to taste with salt and pepper (about 1 teaspoon and 1/2 teaspoon respectively).
Add peas and carrots and stir to combine. Transfer to an 8-10" casserole dish. Arrange tater tots on top and sprinkle with grated cheese. Bake 20-25 minutes, or until cheese melts and tots start to brown, and filling bubbles up the side.