Step 1

In a large saucepan over medium-high, melt butter until foaming. Add mushrooms and cook until the mushrooms have released most of their liquid, about 5 to 7 minutes. the onions, garlic and cook for an additional 5 minutes.

Step 2

Sprinkle in flour and cook for 1 minute. Gradually pour in the chicken stock, bring to simmer, and cook until thickened, about 1 minute.

Step 3

Stir in milk, season to taste with salt and pepper, and simmer for additional 1 minute. Keep warm.

Step 4

Preheat oven to 375 degrees. In a large saucepan, add ground beef and onion and cook until browned, about 5 to 7 minutes. Drain well. Stir in garlic and chili powder until fragrant, about 30 seconds.

Step 5

To the ground beef mixture, add the mushroom sauce, tomatoes, corn, sour cream and 3/4 cup cheddar cheese. Season to taste with salt and pepper. Add the mixture tto a 2-quart casserole pan. Top the mixture with the frozen potato tots and remaining 3/4 cup cheddar cheese.

Step 6

Bake uncovered until the casserole is bubbly and the tots are golden brown, about 40 to 50 minutes. Allow cooling for at least 10 minutes. Garnish with fresh chives.