Preheat your oven to 350°F (175°C). Grease a muffin tin or line it with silicone muffin cups for easy removal.
Gather your ingredients. You'll need eggs, milk (or a milk alternative), salt, pepper, and assorted fillings such as chopped vegetables, cooked meat (like ham, bacon, or sausage), cheese, and herbs.
Crack the eggs into a large mixing bowl. Add milk, salt, and pepper to taste. Whisk the eggs until they are well beaten and the mixture is smooth.
Stir in your chosen fillings into the egg mixture. You can get creative here, mixing and matching ingredients to create different flavor combinations. Just make sure the fillings are cooked and chopped into small pieces for even distribution.
Pour the egg mixture evenly into the prepared muffin cups, filling each cup about 3/4 full. Be careful not to overfill, as the egg muffins will puff up slightly as they bake.
Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the egg muffins are set and slightly golden on top. You can test for doneness by inserting a toothpick into the center of a muffin – if it comes out clean, they're ready.
Once baked, remove the muffin tin from the oven and let the egg muffins cool in the pan for a few minutes. This allows them to set further and makes them easier to remove from the muffin cups.
Serve the egg muffins warm as a delicious breakfast or brunch option. You can also let them cool completely, then store them in an airtight container in the refrigerator for up to 3-4 days. They can be reheated in the microwave or oven for a quick and easy breakfast on busy mornings.