Preheat the oven to 425 degrees.
Cream together sugar and butter for 3-4 minutes. While this is creaming together, sift all the dry ingredients into a large bowl.
Mix in the eggs one at a time into the butter/sugar mixture, followed by the vanilla extract, coffee, and buttermilk.
Once mixed, add in the dry ingredients and mix for 1-2 minutes.
Fold in the dark chocolate chips and mini chocolate chips.
Scoop out 6 tablespoons of batter into each large muffin tin. This will make 6 large muffins.
Bake at 425 degrees for 5 minutes. Then, reduce the heat to 350 degrees and bake for another 18 minutes or until a toothpick comes out clean from the center.
Once out of the oven, press 3-4 dark chocolate chips into the top of each muffin.
Allow the muffins to cool for 5 minutes, then transfer them to a wire rack to finish cooling.
Before serving, add a light dusting of confectioner’s sugar. Enjoy your delicious Double Chocolate Chip Muffins!