Place the almond flour, icing sugar, and Oreo cookie crumbs in a food processor. Process until they are just beginning to clump. Sift and discard any bits that won't pass through the sifter. Set aside.

 

Whip the egg whites until they're the consistency of a loose foam, add in cream of tartar. Continue whipping while slowly adding caster sugar. Whip to a stiff meringue.

 

Fold the dry mixture into the meringue.

 

Pour the batter into a piping bag. Pipe the macaroons onto your baking sheet. Sprinkle with Oreo cookie crumbs if desired.

 

When all your macaroons are piped, hit the baking sheet on the counter at least 3 times to get rid of any air bubbles.

 

Let the macaroons dry at room temperature until dry to the touch for approx. 1 hour. DO NOT skip this step.

 

Once dry, bake macaroons in a preheated 300°F oven until they stick just slightly to the pans. This can be anywhere from 10-20mins depending on your oven and how crowded the macaroons are on the pan.

 

Let cookies cool completely before removing from pans.

 

Cream Oreo filling and butter until smooth, pale and fluffy. Add in the icing sugar and Oreo cookie crumbs and mix until well combined.

 

Pair up macaroon shells by size, pipe buttercream into the centre, sandwich the cookies together and twist.

 

Allow macaroons to chill for at least 24 hours in the fridge. They are best 2/3 days after making them.