Prepare the Ganache: Begin by chopping the white chocolate into small pieces and placing it in a heatproof bowl. In a saucepan, heat 1/2 cup of heavy cream over medium heat until it just begins to simmer, then pour it over the chocolate. Stir until smooth and fully combined; add 1/4 cup of finely crushed Oreo cookie crumbs for that signature flavor. Allow the ganache to cool at room temperature, then refrigerate for at least 30 minutes until set.

Mix the Dry Ingredients: In a medium bowl, sift together 1 cup of almond flour, 1 cup of powdered sugar, and 1/4 cup of Oreo cookie crumbs. Set the mixture aside.

Whip Egg Whites: In a clean, dry mixing bowl, whip 4 large egg whites using an electric mixer on medium speed until they become foamy. Gradually add 1/4 cup of granulated sugar and continue to whisk until you achieve stiff, glossy peaks—this should take about 3 to 5 minutes.

Combine Mixtures: Gently fold the dry ingredients into the whipped egg whites using a spatula. Aim for a smooth batter that flows in a thick ribbon when lifted.

Pipe the Shells: Transfer the macaron batter into a piping bag fitted with a round tip. Pipe small, round circles on a parchment-lined baking sheet. Tap the baking sheet firmly on the counter to release any air bubbles.

Dry the Shells: Allow the piped macarons to rest at room temperature for about 45 minutes or until a thin skin forms on the surface.

Bake: Preheat your oven to 145°C (290°F). Bake the macarons for 14-15 minutes until firm.

Assemble Macarons: Once the shells are cooled, pipe a generous dollop of Oreo ganache onto half the shells and gently sandwich the remaining shells on top.

Mature the Macarons: For the best flavor and texture, refrigerate the filled macarons in an airtight container for at least 24 hours.