6 tbsp unsalted butter – melted and cooled to room temperature, plus a little more for greasing pan if not using liners
1.5 cups all-purpose flour – scooped and leveled
0.67 cups granulated sugar
1.5 tsp baking powder
0.5 tsp fine salt
2 large eggs – at room temperature
0.5 cups whole milk – at room temperature
1.5 tsp vanilla extract
0.33 cups sour cream – at room temperature
0.5 cups mini chocolate chips
Instructions
Preheat the oven to 375°F (190°C). Grease a 24-cup mini muffin pan lightly with butter or line with mini paper liners.
Melt the butter in a small saucepan or in the microwave, then set aside to cool until just warm, about 5 minutes.
In a medium bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and fine salt until well combined.
In a separate large bowl, whisk the eggs until lightly blended, then whisk in the whole milk, vanilla extract, sour cream, and the cooled melted butter until smooth.
Add the dry ingredients to the wet ingredients and stir gently with a spatula just until no dry streaks of flour remain; do not overmix. The batter will be thick.
Fold in the mini chocolate chips with a few gentle strokes until evenly distributed.
Use a small spoon or scoop to divide the batter evenly among the mini muffin cups, filling each about 3/4 full.
Bake the mini muffins on the center rack until they are risen, lightly golden at the edges, and a toothpick inserted in the center comes out clean or with a few moist crumbs, 10–13 minutes.
Remove the pan from the oven and let the muffins cool in the pan for 5 minutes to set.
Carefully transfer the mini muffins to a wire rack and let cool until just warm or at room temperature before serving.