Make macarons batter
Sift the confectioner's sugar with the almond flour in a medium bowl. Combine the egg whites (I) and mix well everything to form a paste. Set aside.
To make the Italian meringue, in a saucepan, bring the water to boil with the sugar. Stir to make sure that the sugar is dissolved. Place the remaining egg whites (II) in the bowl of a stand mixer fitted with a wire whisk. As soon as the sugar syrup reaches a temperature of 239 F (115 C), begin beating the egg whites into stiff peaks. When the syrup reaches 245 F (118 C), with the mixer running at medium speed, gradually pour it into the egg whites in a steady stream. Keep beating about 4-5 minutes or until the meringue has cooled to 122 F (50 C).
Using a silicone spatula, fold a third of Italian meringue into the almond mixture, allowing the paste lose its volume. Then fold in the rest of the Italian meringue in two more additions. Stir gently until the batter is glossy and fluid. Don’t overfold, but fully incorporate your ingredients! The mixture should flow like ribbon and a streak of mixture spread over the surface of the rest of the mixture should disappear after about 30 seconds. Transfer the batter to a piping bag fitted with a plain #11 or #12 pastry tip.
Line baking sheets with silicone mats (or parchment paper). Pipe discs 1 1/2 inches in diameter and 3/4 inches apart on the lined silicone mat. Tap the baking sheets carefully on a worked surface to release trapped air. Set aside at room temperature for 30-60 minutes to allow a crust to form (when you press the surface of one gently it does not break or stick to your finger).
Preheat the oven to 320 F (160 C).
Place the baking sheets in the oven. Bake the macaron shells for 12-14 minutes. Carefully test if the base of the shell is ready by gently lifting one and if it’s still soft and sticking to the baking paper, then it needs to bake for a few minutes longer. After removing the shells from the oven, place them on the work surface and let them cool completely.