Preheat the oven to 425° F. Line every other muffin tin with a muffin liner. This will allow our muffins to bake up with a large top without running into each other.
In a large bowl, stir together the flour, granulated sugar, cocoa powder, baking powder, salt and mixed chocolate chips.
In a separate bowl, combine the eggs, sour cream, canola oil, buttermilk and vanilla extract. This will be fairly thick.
Pour into the dry ingredients and fold until completely combined.
Fill the lined muffin tins full with batter.
Bake at 425° F for 7 minutes and then, while leaving the muffins in the oven, reduce the temperature to 350° F and bake for an additional 20 minutes.
Let them set for 10 minutes before removing from the pan and allowing them to cool on a cooling rack until you are ready to enjoy.
Store at room temp for up to 4 days or in the freezer for up to 3 months. Enjoy!