Preheat your oven to 300°F (150°C) and line two baking sheets with parchment paper.

Sift the super-fine almond flour and powdered sugar together in a large bowl, repeating twice.

Whip the egg whites until frothy, gradually add fine sugar and cream of tartar, and whip until stiff peaks form.

Gently fold the dry mixture into the meringue until it flows like thick lava.

Pipe 1.5-inch circles on the baking sheets and let them sit for 20-30 minutes to form a skin.

Bake the macarons for 15-18 minutes or until they lift easily from the parchment paper.

Cool macarons completely and prepare the filling by heating egg yolks, sugar, and milk, mixing in butter and vanilla.

Pipe the buttercream filling between two shells and refrigerate to meld the flavors.