Preheat the oven to 350°F (180°C). Lightly grease a mini muffin pan.
In a mixing bowl, whisk together ½ cup (100 g) granulated sugar, ½ stick (57 g) unsalted butter, melted, 1 large egg, ¼ cup (60 ml) milk, and 1 teaspoon pure vanilla extract until combined.
In a separate bowl, whisk together 1 cup (120 g) all-purpose flour, ½ teaspoon baking powder, ½ teaspoon salt, and 1 teaspoon ground cinnamon.
Add the dry ingredients to the wet ingredients and whisk until the batter is smooth and thin.
Spoon the batter into the prepared mini muffin pan, filling each well about three-quarters full.
Bake at 350°F (180°C) for 12–15 minutes, or until a toothpick inserted into the center of a muffin comes out clean and the tops are lightly golden.
Remove the pan from the oven. Let the muffins sit in the pan for 2 minutes, then transfer them to a wire rack and cool until warm to the touch (about 3–5 minutes) so they can be handled.
While the muffins cool, prepare the coating: put 3 teaspoons butter, melted, in one shallow bowl. In a second shallow bowl, combine ½ cup (100 g) granulated sugar and 1 teaspoon ground cinnamon; mix until uniform.
Working one warm muffin at a time, dip or brush it in the melted butter to coat all sides, then roll it in the cinnamon‑sugar mixture until evenly coated. Place coated churro bites on a rack or plate to set.
Repeat until all muffins are coated. Serve warm.
Notes
This recipe has been tested using vegetable oil instead of butter, and it also worked fine.