PREHEAT oven to 325° F.
HEAT nonstick skillet over medium heat. COOK the sausage until browned and REMOVE from pan, leaving the rendered fat.
ADD the chopped mushrooms and SAUTÉ until golden brown, STIRRING as needed to evenly cook.
RETURN sausage to the pan and TOSS in cherry tomatoes and butter. WHISK eggs, SEASON with salt and pepper and ADD to pan.
Using a rubber spatula, gently STIR the eggs as they begin to cook, SCRAPING the bottom of the pan and distributing the ingredients evenly. PLACE skillet in the oven and BAKE until set, about 10 minutes.
SLICE into squares the same size as the bread and PLACE between two slices. CUT down the center and SERVE.
Change up the veggies with your favorites, or whatever is in season.
Make sure to use enough butter that your frittata slides easily out of the pan.
This recipe is an excellent source of protein, vitamin A, iron and choline, and a good source of folate.