In medium bowl, sift together almond flour, pistachio flour and powdered sugar twice. Set aside.

In a large mixing bowl with whisk attachment, beat the egg whites on medium speed until foamy. Add cream of tartar and continue to beat. Slowly add sugar one tablespoon at a time. And beat until hard peaks. Add the food coloring (I used Wilton Leaf Green). Beat on medium speed for one more minute. (Watch this meringue video for more information.)

Sift the dry ingredients over the whipped egg whites. Gently fold the mixture running the spatula clockwise from the bottom, up around the sides and cut the batter in half. The batter will look very thick at first, but it will get thinner as you fold. Be careful not to over mix it though. Every so often test the batter to see if it reached the right consistency. To test the batter, drop a small amount of the batter and count to ten. If the edges of the ribbon are dissolved within ten seconds, then the batter is ready. I repeat, do NOT mix again. If you still see edges, fold the batter couple more times and test again. I posted a few pictures above to show you how just a few folding changes the consistency of the batter. This step is so crucial, so please make sure to test often to ensure not to over mix the batter.

Transfer the batter into a pastry bag with a round tip. (I use this Wilton A1 large plain round tip.)

Pipe out 1.5-inch rounds about an inch apart on two baking sheets lined with parchment paper. You should get about roughly 54 shells.

Tap the baking sheets firmly on the counter a few times to get rid of any air bubbles. If you don’t release the air bubbles, they will expand during baking and crack the beautiful macarons shells.

Let the macarons rest and dry for 15-30 minutes. On a humid day, it might take an hour or so. To see if it’s ready to be baked, lightly touch it. If the batter doesn’t stick to your finger, then it’s ready. Preheat the oven to 300°F (150°C).

Bake the macarons for 18-20 minutes. To check the doneness, remove one macaron. If the bottom does not stick, they are done.

Transfer to wire rack to cool for 15 minutes, and then remove from the baking sheets.

While macarons are drying, prepare the pistachio cream. In a small saucepan, combine water and sugar and heat it over medium heat. Stir the mixture until the sugar is completely dissolved. Then bring it to a boil and cook until the syrup reaches 250°F (120°C).

In a mixing bowl with whisk attachment, beat the egg yolks for 2 minutes. While the mixer is running on low, slowly pour the hot syrup into the egg yolks. Increase the speed to medium high, and beat the mixture until it cools down to 104°F (40°C). The mixture will become smooth and white.

Add the butter a tablespoon at a time. Then add the pistachio paste and food coloring, if desired. Continue to beat the cream until nice and smooth.

Transfer the pistachio cream into a pastry bag and fill the macarons. It’s best to serve macarons the next day.

Store the filled macarons in airtight container in the fridge for up to 5 days. You can also freeze the filled macarons in airtight container for up to 5 months.