Start by finely chopping 100 grams of white chocolate and placing it in a heatproof bowl. Heat 50 milliliters of heavy cream on low until it just begins to simmer, then pour it over the chopped chocolate. Let it sit for a couple of minutes before stirring until smooth. Mix in 30 grams of crushed Oreo cookie crumbs, then cover and chill in the refrigerator for at least 30 minutes until it thickens.

In a large mixing bowl, sift together 120 grams of almond flour, 200 grams of powdered sugar, and 30 grams of crushed Oreo cookie crumbs. This step is crucial for a smooth macaron shell, so take your time to ensure there are no lumps. Set the mixture aside.

In a clean, dry mixing bowl, beat 110 grams of egg whites on medium speed until foamy, about 2-3 minutes. Gradually add 50 grams of granulated sugar, increasing to high speed. Continue beating until stiff peaks form, and the meringue is glossy and holds its shape.

Gently fold the sifted dry ingredients into the meringue in three additions using a spatula. Be careful not to deflate the air already incorporated into the egg whites. The batter should achieve a 'ribbon' consistency.

Prepare a baking sheet with parchment paper or a silicone mat. Using a piping bag fitted with a round tip, pipe 1.5-inch circles, leaving about an inch of space between each one. Tap the baking sheet firmly to remove air bubbles. Allow the piped batter to rest for 30 to 60 minutes, until a skin forms on the surface.

Preheat your oven to 145°C (290°F). Once the shells have formed a skin, place the baking sheet in the oven. Bake for 14-15 minutes, until the tops are set and the macarons slightly lift off the parchment without sticking.

Once baked, let the macarons cool completely on the baking sheet for about 10 minutes. Carefully transfer them to a wire rack to cool completely. When cool, take the chilled ganache and pipe a generous dollop on the flat side of half of the macarons. Sandwich them with the other half.