Preheat the oven to 425ºF and spray a muffin tin with cooking spray or line it with paper muffin liners.
Place the butter in a small microwave-safe bowl and melt in the microwave until almost completely melted, then set aside to let cool.
In a large mixing bowl whisk the flour, cocoa, baking powder, baking soda, and salt until well combined. Stir in the sugar and continue to whisk until it's mixed in completely.
Using a separate medium bowl whisk the eggs, buttermilk, canola oil, melted butter, instant coffee, and vanilla extract until smooth. Don't overmix!
Pour the wet mixture into the dry ingredients and use a rubber spatula to fold them together until combined. Fold in the chocolate chips.
Spoon the mixture into the prepared pan, filling the cups almost to the top. Bake for 4 minutes and then reduce the heat to 350ºF without removing the pan or opening the oven. Continue to bake for an additional 12 to 16 minutes, or until a toothpick inserted into the center comes out clean. Transfer to a wire rack and let cool for 10 minutes before removing from the pan.
To store: place the cooled muffins in an air-tight container for up to 2 days or wrap them in plastic wrap individually and freeze them for up to 2 months.