For the donuts:
- 6 tablespoons (85 g) unsalted butter, melted
- ½ cup (100 g) packed light brown sugar
- 1 teaspoon vanilla extract
- 1 large egg
- ½ cup (118 ml) buttermilk
- ½ teaspoon baking powder
- ¼ teaspoon baking soda
- ½ teaspoon kosher salt
- 1 teaspoon freshly grated nutmeg
- 1½ cups (195 g) all-purpose flour
For the cinnamon-sugar:
- ½ cup (113 g) unsalted butter, melted
- ¾ cup (150 g) granulated sugar
- 2¼ teaspoons ground cinnamon
- Heat the oven to 350°F. Generously grease a 24-cup mini-muffin pan with cooking spray or softened butter.
- To make the donuts, whisk the butter, sugar, and vanilla in a large bowl for 30 seconds. Whisk in the egg and then the buttermilk. Sprinkle the baking powder, baking soda, salt, and nutmeg over the bowl, one at a time, vigorously whisking after each. Gently fold in the flour with a flexible spatula until the last streak disappears. Fill each mini cup with one tablespoon of batter, using either a small ice cream scoop or a measuring spoon.
- Bake for 8 to 10 minutes, rotating the pan at the halfway point. The donuts are done when their tops look dry, they bounce back after being lightly pressed, and a wooden skewer inserted in the center of one comes out clean or with a moist crumb or two. Cool them in the pan on a cooling rack only for so long as it takes you to melt the butter and prepare the cinnamon-sugar. Repeat with the remaining batter
- Pour the melted butter in one small bowl and whisk the sugar and cinnamon together in another. Nestle the cooling rack over a baking sheet. Dunk each donut in the butter, lifting it out with a slotted spoon, and then roll it in the cinnamon-sugar, using a large fork or your hands to nudge it around, before transferring it to the cooling rack. Enjoy warm or at room temperature. The donuts will keep in an airtight container on the counter for up to 3 days. Makes about 30 munchkins.