Make Cupcakes: Preheat oven to 350°F (175°C) and line two standard cupcake pans with 18 cupcake liners.

Combine Ingredients: In a large bowl, combine the cake mix, eggs, vegetable oil, and brewed coffee. Stir until well combined.

Fold in Chocolate Chips: Fold in the mini chocolate chips.

Fill Liners: Divide the batter evenly between the cupcake liners, filling each about two-thirds full.

Bake: Bake until a toothpick inserted into the middle of a cupcake comes out clean, 18 to 20 minutes.

Cool: Let the cupcakes cool in the pans for 10 minutes, then transfer them to a cooking rack to cool completely.

Make Frosting: Meanwhile, make the frosting. In a large bowl, combine the softened butter and about half of the powdered sugar. Using a hand mixer, beat until the mixture is smooth.

Add Remaining Ingredients: Add the remaining powdered sugar, heavy cream, espresso powder, and salt. Beat until the mixture is fluffy.

Frost and Garnish: Transfer the frosting to a pastry bag fitted with a large closed star tip (or use a spatula). Pipe the frosting onto the cooled cupcakes. Garnish with chocolate shavings and drizzle with chocolate syrup.

Serve