Preheat the oven to 350F. Line a muffin pan with liners.
Mix the butter, granulated sugar and vanilla extract until light and fluffy.
Mix in the egg and plain Greek yogurt until creamy.
Add in milk. Mix until fully combined.
In another bowl, whisk together the flour, cocoa powder, baking powder, baking soda and salt.
Start adding the flour mixture slowly and alternately with the coffee and mix slowly. Don't over mix the batter.
Once all the ingredients are mixed together, fold in the chocolate chips slowly.
Scoop the batter into the liners using an ice cream scoop, fill each liner ¾ full.
Top with some extra chocolate chips.
Bake in the oven for 18-20 minutes until a toothpick inserted in the muffin comes out clean.
Take the muffins out of the oven. Cool for 20 minutes and the serve.