Here are a few tips to make perfect macarons:
1. Macarons tend to crack when there is a lot of moisture in the air so try to make them on a dry day (avoid rainy days!) It started raining when we were making our macarons and we had probably close to 10% of our macarons crack because of humidity!
2. Separate your egg whites a few days before making the macarons and let them sit in a container, in the refrigerator for a few days. On the morning of your macaron making day, set the egg whites on your counter since they need to be at room temperature for better results.
3. Prepare your filling at least one day before making the shells to ensure it has enough time to cool down and set.
4. To get perfectly round macarons, trace even circles on a parchment paper sheet and place it under your "real" parchment paper sheet as a guide when piping the shells. We fit 48 shells on one large baking tray (6 shells wide by 8 shells long).