Cut the butter into small pieces (about 1 tablespoon each), and place them in a large glass measuring cup with a spout. Microwave the butter at 50% power for 15 seconds at a time until most of it has melted and a few small pieces of butter remain. Stir the butter until the rest has melted.

Preheat oven to 375°F. Line a 12-cup muffin tin with silicone or paper muffin liners. Spray the liners with nonstick cooking spray.

In a medium mixing bowl, combine the melted butter, eggs, milk, and vanilla extract. Whisk until smooth.

In a large mixing bowl, combine the flour, baking powder, sugar, and salt. Whisk until combined. Using your (clean!) hand, make a well in the center of the flour mixture. Pour the egg mixture into the well. Using a rubber spatula, gently stir the ingredients just until all of the flour has been moistened (it’s better to undermix than overmix the batter, so it’s OK if a few lumps remain).

Stir in the optional mix-ins, if using.

Spoon the batter into the muffin liners, filling each about two-thirds full. Ask an adult to bake the muffins for 15 to 20 minutes, or until a toothpick inserted in the center of a muffin comes out clean. Let the muffins cool in the pan until room temperature, then remove the muffins from the liners and eat, or store in a container at room temperature for up to 2 days.

Now that you’ve mastered a basic muffin recipe, it’s time to play! Here are even more ideas for how to fancy-up your muffins with mix-ins and toppings.

Jammy muffins: When filling the muffin liners with batter, fill them halfway, then add 1 teaspoon of your favorite jam or preserves in the middle. Add the rest of the batter, making sure to cover the jam completely.

Lemon-poppy seed muffins: Add 1 tablespoon of finely grated lemon zest to the milk and egg mixture, and stir in 2 tablespoons poppy seeds when combining the wet and dry ingredients.

Whole-wheat muffins: Replace the 2 cups all-purpose flour with ¾ cup whole-wheat flour and 1 cup all-purpose flour.

Funfetti muffins: Fold ½ cup rainbow sprinkles into the batter in Step 5.

Pineapple coconut muffins: Add 1 cup drained, canned pineapple chunks to the wet ingredients and ½ cup coconut flakes to the dry ingredients before combining.

Corn muffins: Replace the 2 cups of all-purpose flour with ¾ cup yellow cornmeal and 1 cup all-purpose flour.