Preheat the oven to 300°F (150°C) and line two baking sheets with parchment paper or silicone mats.
Sift together the Almond Flour and the Powdered Sugar into a large bowl, discarding any large bits; repeat the sifting if needed so the mixture is very fine.
In a clean, dry bowl whip the Egg Whites with a pinch of Salt until foamy. Gradually add the Granulated Sugar while continuing to beat until you have glossy, stiff peaks.
Add a small amount of the Gel Food Coloring to the meringue and fold briefly to incorporate the color evenly.
Fold one-third of the meringue into the dry almond mixture to loosen it, then gently fold in the remaining meringue using a spatula. Work until the batter flows in a thick ribbon and the surface evens out (the macaronage stage)—do not overmix.
Transfer the batter to a piping bag fitted with a round tip and pipe uniform 1-inch rounds onto the prepared sheets, spacing them about 1 inch apart. Tap the baking sheet firmly on the counter a few times to release air bubbles and smooth any peaks.
Allow the piped shells to rest at room temperature for 20–60 minutes, until they form a dry skin and are no longer tacky to the touch.
Bake one sheet at a time in the preheated oven for 12–16 minutes, until the shells have formed feet and are set. Let the shells cool completely on the sheet before removing.
To make the filling, heat the Heavy Cream until it just begins to simmer. Pour the hot cream over chopped Dark Chocolate and let sit for a minute, then stir until smooth. Stir in softened Unsalted Butter until the ganache is glossy and well combined.
Allow the ganache to cool and thicken to a pipeable consistency, then transfer to a piping bag. Pair shells by size, pipe a small dollop of ganache onto the flat side of one shell, and sandwich with its partner.
For best flavor and texture, refrigerate the filled macarons in an airtight container for at least 24 hours to mature, then bring to room temperature before serving.
