Preheat oven to 320F. Separate two eggs and place the whites in the bowl of a stand mixer with the whisk attachment. Add the granulated sugar and begin to mix on low speed.
Mix for 2 minutes at each speed setting, increasing the speed by one after each 2 minutes. Once at max speed continue to mix until stiff peaks form. The mixture should be super thick.
Add food coloring if using and mix to combine.
Cookie Dry Ingredients
While the meringue is mixing, separate the filling (white) from the outer parts (chocolate) of the 12 cookies. Set the white filling aside for later.
Add the cookies to a food processor and grind until a fine powder. Sift the ground cookies and measure 1/3 cup of the sifted cookies into a bowl. If there is not enough and a lot of large cookie chunks, regrind the large chunks until you have 1/3 cup.
Sift the almond flour and combine 1/3 cup of the sifted almond flour with the sifted cookie. Add the sifted powdered sugar and stir to combine.
Dump all of the dry ingredients into the stiff meringue. Fold to combine by using your spatula to scrape around the edge of the bowl and then down through the middle repeatedly.
Once mixed, spoon the mixture into the bottom corner of a plastic bag. I like to use one of my big wine glasses to hold the plastic bag while I spoon the filling into it and it all fits perfectly!
Line a baking sheet with parchment paper. Cut the corner of the plastic bag so there’s about a 1 cm opening, and use the bag to pipe quarter sized circles of cookie onto the parchment paper leaving some room for expansion.
Smack the tray of raw cookies onto the floor or counter at least 3 times to help remove air bubbles. Let the raw cookies sit for 15 minutes before baking to help prevent the cookies from cracking as they expand in the oven.
Bake for 5 minutes on a rack 1/3 of the way from the bottom of the oven. Rotate 180 degrees and cook for 5 more minutes. Remove from the oven and let cool.
Filling
For the filling whip the butter together with the Oreo fillings until you have a smooth paste.
Once the cookies are cool match sets of 2 cookies together that are the same size. Place a dollop of frosting on one of the cookies and gently push the matched cookie on top making a cookie sandwich.