Preheat the oven to 350°F (175°C) and prepare a 12-cup cupcake pan with paper liners.

Whisk dry ingredients: In a bowl, mix together the flour, baking powder, and salt.

Cream butter and sugar: Beat the butter and sugar until smooth and fluffy. Add the eggs one by one, then blend in the vanilla extract.

Mix wet and dry: Gradually combine the dry ingredients with the wet ingredients, alternating with the buttermilk. Gently fold in the crushed Oreos.

Fill the cupcake liners: Spoon the batter into the liners, filling them about two-thirds full.

Bake the cupcakes for 18-20 minutes. Once done, let them sit in the pan for 5 minutes, then carefully move them to a wire rack to finish cooling.

Frost and decorate: Pipe the Oreo buttercream onto the cooled cupcakes and add a whole Oreo on top.