Preheat oven to 400 degrees. Heat your pan (my absolute fave!) on medium heat on stovetop. Add 2 T of the butter to the pan. After butter melts, add onion, sausage and broccoli, and cook for 5-7 minutes. Then add 1 T more of butter and mushrooms to pan. Cook mushrooms for ~ 3 mins.
While pan ingredients are cooking, whisk together eggs, milk, cheese, and salt/pepper in a bowl. Pour egg mixture into pan and spread evenly over the ingredients. Cook on stovetop for 3 minutes (no stirring!) until edges start to set.
Carefully place pan in oven and cook for 10 minutes. The frittata is done when eggs appear set and frittata is separating a bit from the edges of the pan. Let cool a bit, slice, and serve!
🥚 To plate...cut frittata into 6 pie-like slices. You can have your frittata with some toast and/or a yogurt sundae (yogurt, mixed fruit, and drizzle of honey) on the side.🥚 If you don't have some of these ingredients, use what you got. Within reason, you can put almost anything in a frittata. Just note that denser ingredients require a bit more cook time.🥚 Cook the egg mixture on low to medium heat to prevent eggs from browning.🥚 Make sure your skillet is oven-safe before placing your frittata in the oven.