Place the almond meal and icing sugar in a food processor and blitz until well combined and there are no visible lumps. If you're using almond flour, just go ahead and sift it 3 times with the icing sugar
Place the egg whites and optional cream of tartar into a clean stand mixer mixing bowl. Use the whisk attachment to whisk on low-medium until frothy
Gradually add the caster sugar, 1 tablespoon at a time. Mix for 30 seconds until adding the next spoonful. After adding the last spoonful, continue to whisk on medium-high for another 5 minutes. Mixture should be thick and glossy
Add the food colour and whisk again to combine
Remove the bowl from the mixer, then add the almond meal mixture. Use a large silicone spatula to fold the mixture through. Continue to fold the mixture until it is glossy and can form a smooth ribbon figure 8. The figure 8 should slowly melt back into the rest of the mixture -the batter is now ready to pipe
Place a macaron mat onto each of the baking sheets and set aside
Place a 1cm round piping tip into a large piping bag. Twist the the bag and tip to stop the mixture coming out when you pour it into the bag. Place the bag into a tall narrow jug or cup and fold the ends of the bag over to open the bag. Pour the batter into the bag
Pipe small circles onto the tray, to about ⅔ to filling the circles on the mat. I count to 2, then twist and flick the piping bag
Once the shells have all been piped, gently tap the trays onto a covered bench. Rotate the tray to tap both sides. Use a toothpick to pop any remaining holes, then set the trays aside to rest for 30 minutes
While the shells are resting, heat the oven to 150°C or 300° conventional. If using a fan oven, reduce the temperature to 135°
Bake the macarons for 15-18 minutes. Check after 15 minutes -before removing them from the oven, check one of the middle macarons by giving it a wriggle. If it clearly wriggles, give it another 2-3 minutes of baking.
Once baked, slide the silpat macaron mats onto a bench and leave to cool completely, before gently lifting them from the mat. Match up even macaron shells and place into pairs