Allow ingredients to come to room temperature. Then preheat the oven to 170°C/340F. Line a 12 cup muffin tin with cupcake liners.
Toss the vanilla extract and instant coffee or espresso powder into the milk (this helps the instant coffee to dissolve into the milk).
125 grams milk, 1 teaspoon vanilla extract, 1 teaspoon instant coffee or espresso powder
Melt the butter and allow it to cool while continuing with the steps.
60 grams butter
Beat the eggs and sugar until the mixture is light and fluffy - about 3 to 5 minutes using an electric hand mixer or stand mixer.
2 eggs, 150 grams white granulated sugar
Pour in the melted butter and milk. Whisk through to combine.
Sieve in the cocoa powder, flour, baking powder and salt. Whisk until the cake mixture is combined and smooth. No not overmix.
150 grams plain flour, 1½ teaspoon baking powder, ¼ teaspoon table salt, 25 grams unsweetened cocoa powder
Divide the cupcake batter between the 12 liners, filling about ⅔ full. Bake the cupcakes for 18 to 22 minutes or until a toothpick comes out mostly clean. Take out the oven and allow to cool for 5 to 10 minutes before turning out onto a wired cooling rack.