Heat your oven to 300°F. Place the almond flour and the castor sugar in a large mixing bowl and whisk together. Meanwhile, in the bowl of a stand mixer (or using a hand mixer) whisk the egg whites until they form stiff peaks. This should take approximately five minutes.

You will know stiff peaks are formed if you can hold the bowl upside down and nothing comes out! Using a spatula, transfer the egg whites into the bowl with the flour mixture in thirds and fold them together. Once all of the egg white is transferred, add the almond extract and knead by hand.

Using a cookie scoop, scoop the dough and roll into a ball. Cover the dough in powdered sugar, place on a cookie tray lined with either parchment paper or a baking mat, and bake for 30 minutes. The lower temperature is what maintains the soft center of the cookie. Cool for 10 minutes on the cookie sheet, and then serve.