Preheat the oven to 285°F. Line a large baking sheet with parchment paper.

Sift all the dry ingredients into a large bowl and mix well to combine. Set aside.

In a separate bowl, beat egg whites for 3-4 minutes, until stiff peaks form. Stir dry ingredients into the egg whites with a spatula, but be sure not to overmix – the mixture shouldn’t be runny. Fit a large disposable piping bag with a medium tip and transfer the mixture to the piping bag. Pipe small dollops of the mixture onto the baking sheet until you use all the mixure (you should have 30-40 dollops). Bake for 15 minutes.

Cool the cookies and pair the ones of similar size. Spoon 1 teaspoon of melted chocolate on the flat side of a cookie. Top with another half and press gently so that it looks like a mini hamburger. The filling should not ooze out the edges. Repeat with remaining cookies and chocolate, and serve.