Preheat oven to 400.
In a hot skillet, saute the diced onion and mushrooms in a tablespoon or two of oil or butter (not the butter listed in ingredients). Season with salt & pepper and other spices as desired.
Remove veggies from pan. In same pan, brown the ground beef & season according to your tastes.
Once beef is browned, push to one side or remove from the pan. Add in butter and melt.
Add flour to butter and whisk to create a smooth paste. Whisk and cook over medium low heat for a couple minutes.
Then add beef broth and cook and stir until thickened. Now add back the meat, onions, mushrooms. And also stir in sour cream.
Check for seasoning and adjust if necessary.
Pour into a large, greased casserole dish.
Top with the tator tots. Bake at 400F, uncovered for 30-45 minutes or until tots are golden brown and delicious! Let sit for 5-10 minutes before serving.