Preheat and Prepare:
Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
Make the Cupcake Batter:
In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
In another bowl, mix eggs, both sugars, oil, and vanilla until smooth.
Alternate adding the dry ingredients and buttermilk to the wet mixture, stirring just until combined.
Stir in hot water (or coffee), then fold in crushed Oreos.
Bake:
Fill each cupcake liner 2/3 full with batter.
Bake for 18–20 minutes, or until a toothpick inserted in the center comes out clean.
Let cupcakes cool completely before frosting.
Make the Frosting:
Beat butter until creamy. Add powdered sugar gradually, then mix in heavy cream and vanilla.
Beat until fluffy, then fold in finely crushed Oreos.
Transfer frosting to a piping bag with a large star tip.
Decorate:
Pipe generous swirls of cookies & cream frosting onto each cooled cupcake.
Drizzle with chocolate ganache and top with a mini Oreo or Oreo half.
