I'll post the On recipe (french) at some point but my current go to will be the following from Bravetart. Read her post first. What I actually absorb from it is as below. I think at this point I'm going to say it's all technique and less about the recipe.
On my oven (and my oven alone) I have it on the middle shelf at Gas Mark 4. Bravetart lists it as 300 degrees F
I use a normal metal baking tray of a reasonable thickness. It's old and probably slightly warped. There's nothing special and I don't put two trays down. When I cook using the new, thicker and flatter brownie tin to cook some of them on, that works as well.
I cook on baking parchment because that's what I use. I have a sil-pat which I would use but I still haven't cut it to the right size. Good luck!
4 ounces (115g) ground almonds
8 ounces (230g) icing sugar
5 ounces egg whites (144g) (I used fresh in the picture, I've used aged and microwaved before)
2 1/2 ounce (72g) caster sugar
1. Take egg whites and whisk together till frothy and then add caster sugar and mix to a meringue (fairly standard)
2. Put in colouring and whisk at high speed for another minute until you have an even coloured meringue.
3. Take the sieved almonds and icing sugar (I sieve icing sugar first, then almonds into a bowl - note if you have bits that don't go through, weigh the bits and replace with some finer stuff.)
4. Take meringue, chuck it into the bowl of icing sugar and ground almonds.
5. Fold together. It's part fold, part squish. You're not actively trying to keep in as much air as you normally would. I take a spatula and fold from underneath and press the mix into the middle whilst rotating the bowl. Work fast as the mixture collapses in on itself if you take too long. You'll use probably less than 25 strokes before most of it is mixed together but remember to scrape the bottom properly so it's combined. The term is "lava-like". You can do a drop test, but personally I find that if you can get it to barely combined (no stray bits of icing and almond), chuck it into a piping bag with a metal circular nozzle (mine is about 1cm opening). It will get more liquid as you wrangle it in anyway.
6. Pipe onto parchment paper. It helps if you follow a template to make it evenly sized and spaced but I don't always. You just end up with a more mismatched set to match later.
7. To pipe, hold piping bag vertical, squeeze without moving the bag and then stop squeezing before the end. Hopefully you have some kind of "nipple" which then settles in. If you have a stiff mixture like the "On" recipe, stop piping and "cut" the flow off by pulling to one side - I am bad at this.
8. After you've finished piping, start the pre-heating of your oven. 300 F, it's Gas 4 on mine because my oven set up is skewed so I always go 1 gas mark above where I need it, and because I am using the middle rack, it defaults to about 1 gas mark lower than the top rack (use the top and the macarons crack on me, see what I mean about knowing your oven?). Therefore instead of Gas 2 for 300F I use Gas 4.
9. Tap the tray on the table (not always essential tbh), remove any large bubbles you can see with a cocktail stick/toothpick and then leave to stand for about 15min -30 min. I usually do about 15 post me finishing as when I've finished piping the bagful the first tray has probably sat for five/ten minutes already. You also don't want it to stand too long overall.
10. When you put your macarons in, wait about five minutes, look to see if there are feet, open the door, turn the tray, shut the door again. You might not need this. I have a gas, non-fan assisted oven.
11. Keep watching to see if they collapse and give you a skirt instead. If so, tough, it was probably because it was too liquid and you folded it too long. If they crack, it's usually because they were too hot.
12. When you think they are done (18 min for my "normal" sized) open the door and try to peel one off. If it comes off and there is a base on the bottom then it's done. If half the innards fall out then it's not done and shut the door. You can check before hand because if they are really not done, when you touch the top it wobbles a bit as it's essentially a macaroon on jelly legs.
13. Remove from oven, whack in your next tray, cool and sandwich with filling of choice.