Combine Dry Ingredients. In a medium bowl, combing gluten-free flour blend, baking powder, baking soda, and kosher salt. Whisk to combine well and set aside.

Combine Butter & Sugar. In a large mixing bowl, combine melted butter and sugar.

Add Eggs & Vanilla. Then, add the eggs one at a time, beating to fully incorporate each egg before adding the next one. Mix in the vanilla extract.

Mix In Sour Cream & Heavy Cream Next, mix in the sour cream until fully combined. Mix in the heavy cream, and stir until well combined.

Add Dry Ingredients To Wet Ingredients. Gently mix the dry ingredients in until just a few dry, floury patches remain.

Mix In The Chocolate Chips. Add 1/2 cup mini chocolate chips and fold them in until the batter is smooth (no more dry patches!), and the chocolate chips are well distributed.

Let The Batter Rest. This step is important! Let the batter rest for at least 1 hour (up to 2 hours at room temperature or even overnight in the fridge) before scooping. The batter will aerate and get fluffier and thicker. Try not to disturb it, so that it keeps all that lovely air and rise.

Preheat The Oven & Prep The Pan. While the muffin batter is resting, preheat the oven to 425 degrees F. Line a 12-cup muffin pan with parchment paper liners.

Scoop The Muffins & Top With Sugar. The batter will be a bit fluffy and thick. Try not to disturb it as you use a large scoop (a large cookie scoop or an ice cream scoop) to scoop muffin batter into the prepared muffin cups. The batter should fill the muffin cups completely and generously. Sprinkle each muffin with about 1 teaspoon extra mini chocolate chips and some coarse sugar (turbinado sugar or demerara sugar).

Bake The Muffins. Pop the pan in the oven and bake for 5 minutes at 425 degrees. After 5 minutes, reduce the oven temperature to 350 degrees F. and bake another 10-12 minutes, or until the muffins are light golden and baked through. (A toothpick inserted in the center should come out with just a few moist crumbs, but no wet batter). You do NOT need to wait for the oven temperature to reach 350 degrees, just adjust the temperature and keep baking.

Cool The Muffins 2-3 minutes in the muffin pan before transferring to a wire rack to finish cooling.