Prepare the Macaron Shells

1. Preheat the Oven: Preheat your oven to 300°F (150°C). Line two baking sheets with parchment paper.
2. Sift Dry Ingredients: Sift the powdered sugar and almond flour together into a bowl. This step is crucial for a smooth macaron shell, so don’t skip it!
3. Whip the Egg Whites: In a separate, clean bowl, whip the egg whites with a pinch of salt on medium speed until soft peaks form. Gradually add the granulated sugar, and continue whipping until stiff peaks form.
4. Add Vanilla: Gently mix in the vanilla extract.
5. Fold Dry Ingredients: Gently fold the dry ingredients into the whipped egg whites using a spatula. Be careful not to deflate the meringue, but also ensure that the mixture is fully incorporated.
6. Pipe the Shells: Transfer the batter into a piping bag fitted with a round tip. Pipe small circles (about 1.5 inches in diameter) onto the prepared baking sheets, spacing them about 1 inch apart. Tap the sheets gently on the counter to release any air bubbles.
7. Rest the Macarons: Let the piped shells rest for about 30 minutes, or until a skin forms on top. This helps the macarons develop their signature “feet” during baking.
8. Bake: Bake in the preheated oven for 15-20 minutes, or until the shells are firm to the touch. Let the macarons cool completely on the baking sheets before removing them.

Prepare the Oreo Filling

1. Crush the Oreos: Using a food processor or a plastic bag and rolling pin, crush the Oreo cookies into fine crumbs. Set aside.
2. Make the Buttercream: In a bowl, beat the softened butter with powdered sugar and vanilla extract until smooth and creamy. Stir in the crushed Oreos until well combined.
3. Assemble the Filling: Transfer the filling into a piping bag.

Assemble the Macarons

1. Pair the Shells: Once the macaron shells have cooled, pair them up by size.
2. Pipe the Filling: Pipe a generous amount of Oreo filling onto the flat side of one shell in each pair. Gently sandwich the second shell on top, pressing slightly to secure the filling inside.