Step 1

Preheat the oven to 375 degrees Fahrenheit.

Step 2

Add butter to a medium skillet over medium heat. Once melted, add the onion and garlic. Stir until the onion is translucent, about 7 minutes.

Step 3

Mix in the spinach, mushrooms, feta, and 1/2 cup of cheddar. Season with salt and pepper.

Step 4

Beat eggs and milk in a medium bowl. Season with salt and pepper.

Step 5

Spread the spinach filling evenly into the pie shell. Pour in the custard, allowing it to incorporate with the filling.

Step 6

Bake it for 15 minutes. Sprinkle the remaining cheddar on top. Bake it for 35 to 40 minutes more, or until the filling is set. Allow the pie to cool for 10 minutes before serving. Slice it and enjoy!