Preheat your oven to 375°F (190°C).

Grease a 12-cup muffin tin with cooking spray or olive oil.

Prepare the egg mixture

In a large mixing bowl, whisk together the eggs and milk until well combined.

Season with salt and pepper to taste.

Chop the mixed vegetables into small pieces.

If using leafy greens like spinach, make sure to finely chop them.

Divide the chopped vegetables evenly among the greased muffin cups.

If using any optional add-ins like cooked meat or potatoes, distribute them evenly among the cups as well.

Sprinkle shredded cheese on top of the vegetables in each cup.

Carefully pour the egg and milk mixture over the vegetables and cheese in each muffin cup, filling them about 3/4 full.

Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the quiches are set and slightly golden on top.

Once baked, remove the mini quiches from the oven and let them cool in the muffin tin for a few minutes.

Use a butter knife to gently loosen the edges, then transfer the quiches to a wire rack to cool completely.

Serve the mini quiches warm or at room temperature as part of your brunch spread and they make for one of the tastiest healthy breakfast ideas!