Preheat oven to 325°F (160°C). Grease a 9x13 inch baking dish.

In a skillet, cook bacon until crisp. Remove bacon from the skillet and set aside on paper towels to drain. Reserve 1 tablespoon of bacon drippings in the skillet.

Add the sliced mushrooms to the reserved bacon drippings in the skillet. Cook for about 5 minutes until softened. Remove from heat.

Crumble the cooked bacon. In a bowl, combine the crumbled bacon, chopped onion, and cooked mushrooms. Stir to mix well.

In a separate large bowl, whisk together the eggs and sour cream until well blended.

Pour the egg mixture into the prepared baking dish. Evenly distribute the bacon, onion, and mushroom mixture over the eggs. Sprinkle the shredded cheddar cheese on top.

Bake for 30-35 minutes, or until the center is set and a knife inserted near the center comes out clean. Let stand for 5 minutes before serving.