Preheat the oven to 350 degrees
Whisk together the flour, cocoa powder, salt, and baking soda in a mixing bowl
In a separate bowl, whisk together the cane sugar, sour cream, milk, eggs, melted butter, and vanilla extract
Add the dry ingredients to the wet and mix until just combined using a rubber spatula. Do not over mix
Fold in the chocolate chips with the rubber spatula and do not over mix the batter
Line muffin tins with parchment paper muffin liners (this will make about 17 full sized muffins) and distribute the muffin batter into the cups
Top with additional semi sweet chocolate chips
Bake the double chocolate muffins at 350 degrees for 17-20 minutes or until a toothpick inserted comes out clean. Do not over bake as this will result in dry muffins
Transfer muffins to a wire cooling rack to cool completely