Finely chop white chocolate and place in a heatproof bowl. Heat heavy cream in a saucepan until simmering, pour over the chocolate, let sit then stir until smooth. Fold in crushed Oreo cookie crumbs and cool in the refrigerator.

Sift together almond flour, powdered sugar, and crushed Oreo cookie crumbs in a bowl.

Beat egg whites in a mixing bowl until foamy, gradually add granulated sugar, and whisk until firm peaks form.

Gently fold dry ingredients into meringue until smooth and flowing like thick ribbon.

Transfer batter into a piping bag and pipe small circles on a lined baking sheet. Tap to release air bubbles and let rest for 45 minutes.

Preheat oven to 145°C (290°F) and bake macarons for 14-15 minutes.

Once cooled, match shells by size, pipe ganache on half, and sandwich with other half.

Refrigerate filled macarons in an airtight container for at least 24 hours.