Preheat the oven to 375 degrees F and grease a mini muffin pan with nonstick spray.
In a medium bowl, whisk together the flour, sugar, baking powder, and salt.
Gently whisk in the eggs, vanilla, milk, and butter. Fold in the desired mix-in.
Divide batter among the prepared muffin pan. Mini Muffins: Use 1 tablespoon batter in each muffin cup and bake for 12-14 minutes.Standard Muffins: Use just under ¼ cup batter in each muffin and bake for 16-18 minutes. Check for doneness with a cake tester or toothpick. When inserted into the center, it should come out cleanly.
Serve with a dip such as applesauce, nut butter, yogurt, or maple syrup.
