Preheat the oven to 375°F. Place tulip cups (or muffins liners) in the muffin tins.
In a bowl: add flour, cocoa powder, espresso powder, baking powder & baking soda while mixing everything together. (I highly recommend sifting the dry ingredients before adding to the wet ingredients, this will make the batter fluffy and not lumpy).
In a large bowl: beat sugar, eggs and mix. Add oil, vanilla extract, sour cream, salt and mix until well combined.
Combine wet and dry ingredients together. Mix until well combined. Add 1 ½ cups of chocolate chips and fold with spatula.
Divide batter into even portions into 12 muffin tins (should be exactly 12). Add the other ½ cup of chocolate chips on top of the batter.
Bake for 18 minutes. Let the muffins cool in the tin for about 10 minutes and then transfer them to a baking rack to finish cooling completely. Continue with the rest of the muffins.