**Mix Wet Ingredients:** In a large bowl, whisk together the melted butter, sugar, sour cream, milk, eggs, and vanilla.
**Add Bananas:** Mix in the mashed bananas until well combined.
**Combine Dry Ingredients:** In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Add the dry ingredients to the banana mixture and stir until just combined.
**Fold in Chocolate Chips:** Gently fold in the 1 cup of mini chocolate chips.
**Rest the Batter:** Cover the batter with plastic wrap and let it rest at room temperature for 1 hour.
**Preheat Oven:** Preheat the oven to 350°F.
**Prepare Muffin Pans:** Line 2 muffin pans with 14 liners, spacing the liners out so each pan has 7 cups lined.
**Fill Muffin Cups:** After an hour, scoop the batter into the muffin cups, filling each to the top. Sprinkle the remaining ½ cup of mini chocolate chips on top.
**Bake:** Bake for 22-24 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
**Cool:** Let the muffins cool in the pan for 10 minutes, then transfer them to a wire rack to finish cooling.