Prepare two baking sheets by lining them with parchment paper or silicone baking mats.

Sift almond flour, powdered sugar, and crushed Oreos through a fine mesh sieve into a bowl. Repeat one more time to make sure the ingredients are uniformly combined, discarding any larger pieces that don't go through the mesh sieve. Set aside.

In a large bowl, beat the egg whites on medium speed until frothy, about 1 minute, then slowly add the granulated sugar, about 1 tablespoon every 20 seconds or so. Increase the speed to medium-high then continue to beat until stiff peaks form.

Add the sifted almond/Oreo mixture to the stiff egg whites and begin to fold them in by mixing with a spatula from the bottom of the bowl and lifting it up to drop onto the top of the mixture. Continue to pull the spatula through the mixture by hand, lifting and dropping in a j-shaped folding motion until the mixture begins to loosen and reaches a consistency similar to flowing lava. If you lift a spatula fill of batter from the bowl, it should drizzle off in a thick ribbon and melt in on itself within about 10 seconds. If it falls off in blobs, rather than a ribbon, keep mixing the batter. You should be able to make 1 or 2 figure-eight patterns with the ribbon of batter. If the mixture immediately melts in on itself like honey or shampoo, then you have probably mixed a bit too far.

Transfer the macaron batter to a pastry bag fitted with a large round piping tip. Or use a large heavy-duty ziploc bag with one corner cut off. Pipe the macarons into 1 ½" circles on the prepared parchment or silicone-lined baking sheets, spacing them a couple inches apart. When the trays are filled, rap them a few times on the counter to help remove air bubbles from the shells, then let them sit out for 30-60 minutes until the tops are dry to the touch and don't stick to your finger.

Preheat oven to 300 degrees F. Bake one sheet of macaron shells at a time for 16-18 minutes. Cool completely on the baking sheet before attempting to remove the macaron shells from the pan.

Meanwhile, make the ganache by combining the white chocolate chipsin a medium bowl. Heat the cream in a microwave-safe bowl for 1 minute, then pour over the white chocolate and let it sit for 5 minutes without stirring. Stir well and reheat in short 15-second bursts in the microwave until fully melted and smooth, if needed. Stir in crushed Oreo crumbs, then refrigerate for 30 minutes until thickened enough to pipe into the macaron shells.

To fill the macaron shells, transfer the Oreo white chocolate ganache to a bag fitted with a small round tip or a ziploc bag with one corner cut off. Pipe enough to fill the centers of half of the macaron shells. Match with the remaining macaron shells.