1 1/2 cups all-purpose flour
1/3 cup sugar 1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1/4 teaspoon salt
1/2 cup (1 stick) unsalted butter
1 cup yogurt (any flavor that corresponds with your mix-ins will work nicely, but I prefer vanilla flavored)
1 large egg
1 teaspoon vanilla
Turbinado or sanding sugar for sprinkling (optional)
Preheat oven to 400 degrees F and line 12 (1/3-cup) muffin cups with paper liners.
Into a bowl, sift together flour, sugar, baking powder, baking soda, and salt. Melt butter and in a small bowl whisk together with yogurt, egg, and vanilla. Stir butter mixture (and additional ingredients; see note, below) into flour mixture until just combined. Divide the batter among muffin cups (this batter is thick and will not run easily like other muffin batters), sprinkle with a pinch of sanding sugar, and bake in middle of oven until golden and a tester comes out clean, about 20 minutes. Flavor the basic muffin batter above by adding, for example: 1 chopped banana and 3/4 cup semisweet chocolate chips; or 1 cup toasted almonds, 3/4 cup dried cranberries, and 1/4 teaspoon almond extract; or 1 cup chopped drained canned pineapple and 1 cup sweetened flaked coconut; or 1 cup chopped dried apricots and 1 tablespoon poppy seeds, 1 3/4 cups fresh berries, or 2-3 teaspoons matcha green tea powder.
Do it! You know you want to! ^_^