Preheat the oven to 180°C (350°F) and line 2 cupcake trays with 24 cupcake papers.
Add the eggs, sugar, and oil to a bowl of an electric mixer fitted with a whisk attachment and beat at medium-high speed until well combined—about 2 minutes.
Sift together the flour, cocoa powder, and salt. Add the dry ingredients to the egg mixture, and beat at medium speed until just combined. The mixture will be thick.
In a jug mix together the milk, brewed coffee, and vanilla. Slowly pour this into the egg and flour mixture, with the mixer’s motor running at low speed. Continually scrape down the sides of the bowl while mixing to ensure a lump-free cupcake batter.
Fill each cupcake liner with chocolate batter, about ¾ of the way up the paper. Bake in a preheated oven at 180°C (350°F) for about 12 – 15 minutes or until a toothpick inserted into the cupcake comes out clean. Cool on a wire rack.
Vanilla Buttercream Frosting
In a bowl of a stand mixer fitted with a paddle attachment, add the butter and icing sugar. Beat until the mixture looks like fine sand.
Combine the milk and vanilla extract, and with the mixer running add this to the icing sugar mixture one tablespoon at a time.
Once all of the milk has been added, scrape down the sides of the bowl and beat at medium-high speed until light and fluffy. About 5 to 10 minutes.
Fill a piping bag with the buttercream and decorate the cooled cupcakes, enjoy!