Preheat oven to 425ºF, and line a 12-cup muffin pan with paper liners or grease with cooking spray; set aside.
In a large bowl, sift flour, sugar, cocoa powder, baking powder, baking soda, salt, and instant espresso coffee; whisk and set aside.
In another bowl, mix beaten eggs with sour cream, milk, oil, and extract. Add wet ingredients to dry ingredients. Stir until just combined. Fold in 1 ½ cups chocolate chips until evenly distributed.
Spoon the batter into the prepared muffin pan until almost to the top. Sprinkle a few chocolate chips on top of muffins.
Transfer to the preheated oven and bake for 5 minutes.
Reduce the temperature to 350ºF and continue baking for 16 to 18 minutes, or until a cake tester inserted in the center comes out clean with just a few crumbs.
Remove from the heat, allow the muffins to cool in the pan before unmolding and transferring them to a wire rack to finish cooling.
Place leftovers in a container and store on the counter for 5 days or in the fridge for a week. They can be frozen for up to 3 months.