Chocolate Ganache (Prepared the day before)

1. Place the chopped chocolate in a heatproof bowl.
2. Heat half of the heavy cream in a saucepan over medium heat until it just starts to simmer.
3. Pour the hot cream over the chocolate all at once and let it sit for a few moments before stirring until smooth.
4. Add the other half of the cold heavy cream and mix again until fully incorporated into the ganache.
5. Use an immersion blender to smooth out the ganache, cover it directly with plastic wrap, and let it cool for 4-6 hours (overnight if possible).

Marble Cupcakes

1. Preheat the oven to 180°C (350°F) and line a cupcake pan with paper liners.
2. In a bowl, sift together the dry ingredients: flour, baking powder, baking soda, and salt.
3. In a large bowl, cream together the softened (or cooled melted) butter and sugar using an electric mixer for 2-3 minutes.
4. Incorporate the eggs and vanilla, beating again for 2-3 minutes.
5. Gradually fold in the dry ingredients and milk alternately with a spatula until the batter is smooth.
6. Divide the batter in half and mix cocoa powder into one half.
7. Spoon dollops of both batters into the cupcake liners, then swirl with a knife or toothpick to create a marbled effect.
8. Bake for about 18 minutes or until golden and cooked through.
9. Allow to cool briefly, then transfer to a wire rack to cool completely.

Assembly

1. Whip the cooled ganache with an electric mixer on medium speed for about 1 minute until creamy and firm.
2. Transfer the whipped ganache to a piping bag fitted with a decorative tip and pipe swirls on top of the marble cupcakes.
3. Sprinkle with chocolate shavings and refrigerate for 1 hour before serving.