Preheat the oven to 350°F. Spritz 10 muffin cups liberally with cooking spray. Set aside
In a medium bowl whisk together the eggs, heavy cream, grated Parmesan cheese, salt, pepper, garlic powder, ground mustard and a dash of nutmeg.
In a medium skillet over medium-high heat cook the onion, diced bell peppers, and mushrooms with butter until softened and browned. Around 3-5 minutes.
Divide the cooked vegetables between the muffin cups. Sprinkle with 1/2 of the shredded Colby-Jack cheese.
Fill the muffin cups 2/3 full with the beaten eggs. Sprinkle each with the remaining shredded cheese.
Bake for 18-20 minutes until puffy, lightly golden brown and the centers are set when the pan is gently shaken. (The eggs will deflate slightly when removing from the oven.)
Serve immediately.
Notes
Veggies - You can adapt the vegetables in the egg filling for these mini quiche to suit your own taste. You could use jalapeno pepper or poblano peppers in place of green peppers for extra spice. You could also use chopped spinach or steamed broccoli, chopped into small pieces.
Cheese - You can adapt this recipe using your favorite flavor of shredded cheese. You can use sharp cheddar cheese, gruyere cheese, swiss cheese or pepper jack cheese.
Low Carb - These quiche are ideal for low carb and keto meal options, as they're naturally gluten-free with no crust. You can switch up the flavor by changing the ingredients and shredded cheese.
Protein - You could also add cubed ham, or cooked crispy bacon or use breakfast sausage in the filling.
Heavy Cream - You could make these dairy-free using almond milk or oat milk as an alternative in place of cream.
Fresh Herbs - You can add parsley, basil, rosemary or thyme.
Customize - You could make as many different flavors by adjusting the mix-ins according to the preference of those your feeding. The added bonus is; they can all be baked at the same time.
The Quiche Settle After Baking - The mini quiche will puff up while baking and will naturally settle once cooled.
Alternate Pan - If you want to make bite-size crustless mini quiche, you can divide the filling in a 24 cup mini muffin pan. The baking time will be shorter, so adjust as needed.