Line baking sheets with parchment or silicone mats.
Grind cookies to fine crumbs in a food processor, blender or with a rolling pin. *2*
Sift 40g of the crumbs (5 cookies worth), almond meal and powdered sugar into a large bowl. The cookie crumbs may need to be ground a few more times to get it through the sieve, but just be patient! Gently whisk together to fully incorporate.
With a hand or stand mixer whip egg whites on high until foamy, about 1 minute. Gradually add granulated sugar and continue to beat until stiff peaks form, about 4 minutes. *3**4*
With a rubber spatula, fold meringue mixture into dry ingredients and continue folding until a steady ribbon of batter slowly falls off the spatula. *5*
Spoon batter into a piping bag fit with an open circle tip. Pipe 1 1/2” circles onto the baking sheets. If desired, sift some extra cookie crumbs on top of the piped circles for decoration.
Bang baking sheets firmly on a hard surface a couple of times to release air bubbles.
Let sheets sit out for an hour to dry out, until a light skin forms on top of the macarons.
In the meantime, prepare the cookie butter. In a food processor, pulse together 140g cookie crumbs, milk and butter until a paste or “butter” forms. Spoon into a separate piping bag and set aside.
Bake macarons at 350 for 16-18 minutes, rotating halfway through. Macarons should not be browned. They should form “feet” that is a ruffle that goes around the bottom of each shell. You can tell the macarons are done if you touch the top of the macarons and they don’t move or squish down on their “feet” at all.
Let macarons cool completely before filling.
Once cool, pipe cookie butter on inside of one macaron shell and sandwich with another.
Almond meal and almond flour are interchangeable. You can use either one!
If you don’t have a food processor or blender, you can always put the cookies in a Ziploc bag and smash with a rolling pin. But just make sure that you get the crumbs fine enough!
A hand mixer will work just as well, but may take a little longer. It will also take a bit longer if it’s humid out (aka NYC in June, ugh!)
Stiff peaks should mean that you can (hypothetically) flip the bowl upside down and have nothing fall out.
To test this, you should be able to draw a figure 8 with the batter, and then after a while it’ll slowly disappear into itself.