Instructions

1. Preheat oven to 300Fº (150Cº, without convection). Line two baking trays with parchment paper. Prepare a medium size pastry bag fitted with a plain tip (1/2 to 3/4 inch opening). To ensure all the macarons have approximately the same size, I made a template that you can print out, and line this template under parchment paper to help you pipe macarons. Use two A4 templates to cover the whole half sheet tray.
2. Put egg whites, granulated sugar and salt in the bowl of an electric mixer fitted with whisk attachment. Whip on medium-low (level 4 on a Kitchen-aid) for 3 minutes, then medium-high (level 6) for 3 minutes, and then on high (level 8) for another 3 minutes. Add gel food color or flavor (vanilla extract, etc) if use any, and beat on the highest setting (level 10) for 1 minute. We want a very dry and stiff meringue. An easy way to check: if there is a big clump of meringue stuck in the center of your whisk attachment, then you are doing it right.
3. Sift the almond flour and icing sugar together, if necessary, use a small food processor or a coffee grinder to process the grainy leftover that cannot go through the sieve, until no more than 1 tablespoon of mixture left.
4. Pour the almond sugar mixture into the bowl of meringue. To incorporate dry ingredients into the meringue, you need to use a folding motion and with each fold turn the bowl counterclockwise one quarter turn. This is also called "macaronage", which is essentially deflating the meringue while mixing everything together. Don't be too gentle. You need about 30-35 folds/turns to reach a lava-like consistency, means when you scoop out some batter, it will drip slowly like a ribbon. Try paying attention after about 25 folds and evaluate carefully after that, one fold at a time. The batter should not be runny like pancake batter (overmixed); or the dripped batter just mounts there and won't incorporate (undermixed).
5. Now, put the mixture into the pastry bag, put your template under the parchment paper and pipe out the macaron circles. Each circle should keep its form. (If it ooze out and spread right away when you pipe, you probably overmixed.) It is very important to bang the baking tray on the kitchen counter 3-5 times to get rid of excessive air, otherwise macarons will crack. After the banging, the circles should spend a little and the little dots on the macarons due to the piping tip should have disappeared too. You don't need to let the macarons rest before baking, it won't save the undermixed or overmixed batter. (But this is a so popular recommendation all over the internet, I guess it may work if your batter is only slightly overmixed, like 2 folds more than necessary.)
6. Bake at 300Fº (150Cº) without convection about 18 minutes. You will see the feet start to develop after about 4 minutes of baking. Please test your oven temperature before baking. Macarons need precise temperature. 5 degree of difference may result some hollow macarons. And personally I have more success baking macarons without convection function, but it could be different if you have a commercial oven.
7. After 18 minutes (you should smell them by now), open the oven door and lift one macaron shell, if you can peel it off easily then take the tray out of oven. If half of the macaron is sticking to the paper you need a few more minutes. Let macarons cool completely before you peel them off the parchment paper. Fill them with you favorite filling and enjoy! Although the macarons are better 24 hours after you fill them, make them more chewy and give the shells the time to absorb more flavor from the filling.
8. Store macarons in an airtight container in the fridge to avoid off flavor. Remove them form fridge 15 minutes before serving, so they can come to room temperature. Macarons freeze really well, if kept in an airtight container they can stay in the freeze for at least 1 month, ours are normally already eaten long before. Just remember to leave them out at room temperature for about 20 minutes before serving.