Preheat oven to 400°F. Lightly grease 18 muffin cups or cupcake liners with vegetable cooking spray. Set aside.
In a large mixing bowl whisk together the flour, cocoa powder, salt, baking powder, baking soda and sugar. Make a well in the center.
In a small mixing bowl combine the sour cream, melted butter, vanilla, milk and eggs. Pour the sour cream mixture into the flour and sugar mixture. Fold together with the spatula until the dry ingredients are just moistened. It may seem very thick and dry, just keep folding! It will come together. Add 1 ½ cups of the mini chocolate chips to the batter and gently fold to combine. Divide the batter between the 18 muffin wells or paper liners. I use a heaping ice cream scoop to portion out the batter. Allow the unbaked muffins to rest at room temperature for 15-20 minutes before baking.
Sprinkle the tops of the unbaked muffins with the remaining mini chocolate chips (mounded in the center) and then sprinkle with coarse sugar, if desired. Bake at 400°F for 16-20 minutes or until a toothpick inserted in the center comes out with no wet batter; moist crumbs are okay. Cool the muffins in the pan on a rack for 5 minutes, then remove to a wire rack to cool completely. Serve slightly warm if desired.
Notes
These muffins are best served the day they are made but keep well a day or two in an airtight container at room temperature.Recommended substitutions:
Substitute regular size chocolate chips for the minis if desired. Dark chocolate, milk chocolate, semisweet or bittersweet chips are all good in these muffins.
Replace the sour cream with Greek Yogurt if desired but I recommend using full fat yogurt.
Top with your favorite chopped nuts in place of the mini chocolate chips.
Add 1 tablespoon black cocoa powder in place of 1 tablespoon natural cocoa for a beautiful dark color and rich chocolate taste.
Nutrition information is calculated using an ingredient database and should be considered an estimate. When multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.