Spray a piece of tin foil with cooking spray, press it gently on top of the frozen pie crust, and place it into the oven to bake for 10 minutes. Remove the foil and continue to bake for 3-5 minutes. Remove from the oven. Place the tin foil on the bottom of a baking sheet. Place the pie crust on top.
Cook the sausage links in a skillet over medium heat until just cooked and browned on the outside—they will finish cooking in the oven. Place on a paper towel to drain grease then cut into bites. Remove the sausage grease from the pan and add olive oil.
Once the pan is hot, add the mushrooms. Cook without stirring for 2 minutes then stir and continue cooking for a minute or two. Remove from the heat. Season with sea salt and freshly cracked pepper, to taste.
Combine the eggs, milk, sea salt, and freshly cracked pepper, to taste, in a bowl and whisk until very well combined.
Sprinkle most of the sausage in the bottom of the pie crust followed by most of the mushrooms and cheese.
Carefully place into the oven and bake for 30-35 minutes, or until the top is set and not wiggly and the eggs are cooked through. Don’t overcook!