Preheat the oven to 300°F and prepare a baking sheet with parchment paper or a silicone mat.
Mix the almond flour and powdered sugar in a bowl and set aside.
Pour the first bowl of egg whites in a stand mixer and start mixing at a slow speed.
While the egg whites are mixing, pour the water and the granulated sugar into a saucepan. Heat the mixture until it reaches about 243°F, using a thermometer, then pour the heated mixture into the mixing bowl with the egg whites.
Let it mix at full speed for about 5 minutes and then voilà! Your Italian meringue is ready.
While your meringue is still mixing, pour the second set of egg whites in the bowl that contains almond flour and the powdered sugar from the first step. Start mixing vigorously until you get a homogeneous paste called “almond batter”.
Now pour your finished Italian meringue into the almond batter. Mix it together. Add the food coloring.
This step is called “macaronage”. It’s the action of mixing the almond batter with the Italian meringue. The objective here is to get a shiny and glossy batter.
Once your batter is shiny and glossy, pour it into an 18 inch piping bag with piping tips. Use either a silicone mat or parchment paper to pipe your macarons shells.
Let your macarons shells dry for about 20 minutes after piping.
Place the baking pan sheets into the oven for 15 minutes at 300°F.
Let the shells cool down until they reach room temperature. Only then should you retrieve it from the silicone mat or parchment paper (to avoid the shells sticking to it).