Preheat the oven to 275°F. Line a heavy, rimmed metal baking sheet with a silicone baking mat (Silpat) or high-quality parchment paper.

In the impeccably clean bowl of a stand mixer, beat the room-temperature egg whites on medium speed until foamy.

Gradually add the granulated sugar and increase the speed to high. Beat continuously until stiff, glossy peaks form, about 5 minutes.

During the final moments of mixing, use a toothpick to transfer the gel food coloring into the meringue, pulsing the mixer just until the color is evenly distributed.

In a separate bowl, sift the confectioners' sugar, almond flour, and kosher salt together through a fine-mesh sieve. Discard any large almond pieces that do not pass through. Sift the entire mixture a second time to ensure absolute aeration (the tant pour tant).

Gently pour the sifted dry ingredients into the stiff meringue.

Using a flexible silicone spatula, fold the mixture together by scraping around the edge of the bowl and pressing down through the center (the macaronage).

Continue folding strictly until the batter is smooth, shiny, and falls slowly off the lifted spatula in a continuous, thick ribbon (approximately 50 deliberate turns). Do not overmix, or the batter will become too loose.

Transfer the batter to a large piping bag fitted with a round ½-inch tip.

Hold the bag completely vertical and pipe the batter onto the prepared Silpat liner, forming uniform 1-inch circles spaced 2 inches apart.

Firmly tap the baking sheet against the counter 8 to 10 times to force any trapped air bubbles to the surface and pop them.

Allow the piped macarons to rest undisturbed at room temperature for 30 minutes. This critical phase allows a dull, dry "skin" to form on the surface, which forces the cookie to rise upward in the oven and develop its signature ruffled base (pieds).

Bake in the preheated 275°F oven for 9 to 10 minutes.

Quickly rotate the baking sheet 180 degrees to ensure even heat distribution, and bake for an additional 10 minutes, or until the shells are shiny and the ruffled "feet" have fully formed.

Remove from the oven and allow the shells to cool completely on the Silpat before attempting to lift them with a thin spatula.

While the shells cool, prepare the ganache. Microwave the bittersweet chocolate chips and heavy whipping cream together in 30-second bursts, stirring until completely melted, smooth, and spreadable.

Match the cooled macaron shells into pairs of equal size. Pipe or spread a dollop of the rich chocolate ganache onto the flat side of one shell, and gently press the second shell on top to seal the sandwich.