8 tablespoons (1 stick) unsalted butter, melted and slightly cooled
1 large egg
1 cup of milk
1⁄2 cup of sugar
1 tablespoon of baking powder
1⁄4 teaspoon of salt
2 cups of flour
Preheat the oven to 375 degrees. Line the wells (12) of a standard-size muffin pan with baking paper liners.
Pour the melted butter into a mixing bowl; whisk in the egg until thoroughly blended and then whisk in the milk. (At this point, you would also mix in additions such as lemon zest and/or vanilla or almond extract.) Whisk in the sugar.
Add the baking powder, salt and one-third of the flour, whisking until completely incorporated. Whisk in another third of the flour. Use a rubber spatula to fold in the last of the flour to form a thick, mostly smooth batter. Gently fold in any add-ins to the batter, if using, such as blueberries and chocolate chips.
Distribute the batter evenly among the wells. (A No. 16 disher makes quick work of this, or you can use a 1/4-cup measure.) Bake (middle rack) for about 20 minutes, until the muffins have risen well and are golden; the tip of a sharp knife inserted into the center of one should come out clean. Transfer to a wire rack to cool (in the pan) briefly if serving right away, or cool completely if storing.
VARIATIONS: For blueberry muffins, add 1 teaspoon finely grated lemon zest to the liquids. After mixing the batter, fold in 1 1/2 cups rinsed, dried and picked-over (or frozen) blueberries. Use 2 tablespoons of sugar mixed with 1/4 teaspoon ground cinnamon to sprinkle over the tops of the muffins before baking.
For lemon poppy seed muffins, add 1 tablespoon finely grated lemon zest to the liquids. Mix in 2 tablespoons poppy seeds after the last addition of flour.
For chocolate chip muffins, add 2 teaspoons vanilla extract to the liquids. After mixing the batter, fold in 1 cup of your choice of chocolate chips. Sprinkle the tops of the muffins with sugar (2 tablespoons total) before baking.
To make old-fashioned jam muffins, add 2 teaspoons vanilla extract and 2 teaspoons finely grated lemon zest to the liquids. Fill the paper liners in the pan halfway with batter and dollop about a teaspoon of your favorite jam or preserves in the center. Add the rest of the batter, being careful to cover the jam completely.