Line a 12-cup muffin tray with only 6 liners. Leave a space between each liner to allow the muffin to rise higher. Set the tray aside.
Whisk flour, baking powder, baking soda, and salt in a small bowl. Set aside.
1 cup + 1 tablespoon all-purpose flour (128 grams), 1/2 tablespoon baking powder, 1/2 teaspoon baking soda, 1/4 teaspoon salt
In another bowl, add the melted butter and sugar into a bowl. Whisk until combined. Then add an egg, vanilla, sour cream and buttermilk. Mix until everything is incoporated
1/4 cup unsalted butter, 1/2 cup granulated sugar, 1 large egg, 1/2 teaspoon vanilla extract, 2 tablespoons sour cream, 1/2 cup buttermilk
Add the flour mixture to the bowl and gently fold the batter until combined. (Avoid overmixing- a few streaks of flour in the batter is fine). Add mini chocolate chips and fold.
1/3 cup mini chocolate chips
Cover the bowl with a kitchen cloth or plastic wrap and allow the batter to rest for 15 minutes. Preheat the oven to 425℉ (218℃).
Evenly distribute the batter into 6 muffin tins. Sprinkle turbinado sugar and extra mini chocolate chips on top.
1 tablespoon turbinado sugar
Place the muffin tray into the oven and bake for 5 minutes, then lower the heat to 350℉ (176℃) for 15-18 minutes or until a toothpick comes out clean.