Preheat oven to 315 degrees F.
Cover a large baking sheet with a silicone mat (parchment paper is okay too - but a silicone mat is preferable). Set aside.
Add almond flour and powdered sugar to a food processor and process for 30 seconds. Sift mixture through a strainer (discard any bits too large to pass through strainer, or reprocess mixture and sift again). Set aside.
Using a standing mixer, add egg whites and sugar to the mixing bowl and mix on medium for 2 minutes. After 2 minutes, increase mixer to medium-high speed for another 2 minutes, and then switch the mixer to high for another 2 minutes (always set your timer). After mixing you should have a beautiful white mixture with stiff peaks.
Add food coloring and mix on low until desired color.
Add the almond flour mixture to the egg white mixture and gently fold until well combined. It will take you about a minute to fold everything together. You'll know the mixture is good when you can hold up the spatula and the mixture ribbons off it smoothly. It will take about 60-70 folds.
Add mixture to a piping bag with a 1" round tip.
Holding the piping bag upright, pipe the mixture to form small round circles. I usually count to 3 (1-2-3) as I pipe. The cookies are meant to be small (about 1-2" wide).
Once mixture is piped into small circles, gently bang the cookie sheet against the counter 3-4 times to remove any air bubbles.
Allow macarons to sit, untouched, for 20-25 minutes. The macarons will form a protective skin over them. You can gently touch the macarons after 20-25 minutes and if the macaron is not wet to the touch, you can bake them.
Bake for about 11 minutes, rotating the cookie sheet halfway through. Do NOT over bake.
Allow cookies to cool for 15 minutes before handling. Use a flat spatula to gently loosen any stuck cookies.
Allow cookies to fully cool before filling.
To prepare the chocolate ganache, heat heavy cream in a small saucepan over medium-high heat. Once cream begins to bubble, lower heat to medium and add chocolate. Stir constantly. Once chocolate is melted, add butter and continue to stir until well combined. Remove from heat.
Allow mixture to cool in the fridge for 30+ minutes before piping. The mixture will harden over time and once it looks and spreads like frosting, it's ready.
Add ganache to a piping bag with a 1" tip and pipe ganache into the center of the bottom of one macaron, than place a second macaron on top of the ganache to form a sandwich.
Place macarons in the fridge for 1-2 hours before eating (this allows the ganache time to firm up). The macarons taste best after refrigeration overnight, so plan ahead.