Preheat oven: Heat your oven to 350°F (175°C) and line a muffin tin with paper liners.
Mix dry ingredients: In a large bowl, whisk flour, cocoa powder, sugar, baking powder, baking soda, and salt.
Mix wet ingredients: In another bowl, combine eggs, brewed coffee, milk, oil, and vanilla. Mix well.
Combine wet and dry: Pour the wet mixture into the dry ingredients, stirring until just combined.
Add chocolate chips: Fold in the chocolate chips for that extra chocolatey goodness.
Fill muffin tin: Spoon the batter into each muffin liner, filling about ¾ of the way full.
Bake: Bake for 18-20 minutes, until a toothpick inserted comes out clean.
Cool: Let muffins cool in the tin for 5 minutes, then transfer to a cooling rack.