01 -
Preheat oven to 175°C. Line a standard 12-cup muffin tin with paper liners.
02 -
In a large bowl, whisk together flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt. Add buttermilk, oil, egg, and vanilla extract. Whisk until a smooth batter forms.
03 -
Gradually pour boiling water into the batter, whisking until fully combined and smooth.
04 -
Divide batter evenly among liners, filling each about two-thirds full. Bake for 18 to 20 minutes or until a tester inserted into the center emerges clean. Allow cupcakes to cool completely in the tin, approximately 1 hour.
05 -
In a stand mixer fitted with a whisk attachment (or using an electric mixer), beat powdered sugar, butter, vanilla extract, and salt on medium-high speed until the frosting is bright white and completely smooth, about 2 to 3 minutes. Tint frosting with green food coloring until desired intensity is achieved, beating well after each addition.
06 -
Transfer frosting to a piping bag fitted with a small round tip. Pipe a small mound in the center of each cupcake, then pipe two vertical lines down the middle, followed by squiggly lines on both sides, emulating a brain's form.
07 -
Drizzle a small amount of red decorating gel over each cupcake, letting it settle into the piping for a gory effect. Refrigerate cupcakes if not serving immediately.