Recipe is for 20 macaroons, that's 40 half shells.
For more precise calculations, according to the number of egg-whites you have: please note that for 1 egg white (35 g) you should use 75 g icing sugar and 40 g ground almonds. Allow me to insist on using precise measures for the ingredients in this recipe. I suggest you really weigh everything rather than using volumes, even if you are unused to doing this.
Macarons are always better (smoother) after a night sealed in a box in the fridge.
This recipe can be varied ad infinitum with different fillings and/or colours. For fruit for example, following the basic principles of the recipe you can try: apricot, lime, blackcurrant (mmm!), strawberry, etc... On this page
you will find some ideas. I have noticed that to get the full "macaron effect", you need to serve several colours and flavours at the same time. Your guests (and you) will be delighted.
I think nevertheless that macarons are improved when their filling is a little tangy, fruity, to contrast strongly with their very sweet taste.
If you encounter problems, here are some mistakes which all beginners make (and me most of all):
- Not sieving ground almonds and icing sugar => macarons with blisters, lumps of almonds or sugar.
- Poor mixing of egg-whites and dry ingredients => uneven macarons, almond cakes rather than macarons
- Not waiting the 30 minutes to "form crust" => macarons cracked, insufficiently risen or rounded
- Undercooking => macarons too soft, impossible to remove from baking sheet
- Overcooking => dry macarons
- Trying to remove macarons from baking sheet before completely cooled => macarons break up or split in two
- My macarons are brown despite my green (or other) food colouring => overcooking