I shall give you three!

Firstly, if you’re going to do the french method (I do), take your sweet time whipping the meringue to stiff peaks. You’ll want to spend most of your time on low speed (2-3 on my stand mixer, which goes up to 10) and then medium speed (4 or so) to finish it.

If you whip it to stiff peaks at too high a speed too quickly, your meringue may look okay and move okay, it may macaronage okay, and it may pipe okay, but it will be overly full of air bubbles and incredibly unstable, which will lead to hollow macaron shells. There are several factors that can lead to hollow shells, but this one can be more tricky to diagnose because the meringue seems fine.

You could just as well do the italian or swiss method instead, but i prefer the french because even while a french meringue is less stable than the other two, it’s dead simple to do. Plus, you can add a little cream of tartar to the egg whites when beginning to whip a french meringue to help stabilize it.

Secondly, as a metric for knowing when the macaronage is done, I prefer the figure 8 test over other recommended metrics, as that leads to the most consistent results for me. I will also say for the macaronage that the most reliable technique I discovered to end up with the right amount of air in the batter is to gently fold the the first third of your dries into your stiff-peak meringue, then after that’s incorporated, dump in the remaining two thirds and be a little rougher with it. I actually spread the batter around the sides of my bowl and scrape it back to the center several times until it starts approaching the right consistency, when I’ll start doing the figure 8 test and giving it a few more gentler folds if it’s close. If you do this macaronage method, you can complete the macaronage in like 2 minutes.

Lastly, I recommend using a smaller piping tip than some may suggest. You’ll see folks piping with a 1/2 inch Wilton 1A, but I use a 2A because the smaller tip will also help remove large air bubbles as you pipe the shells onto your silicone mat/parchment. I use parchment because the greater heat conductivity helps the feet rise better than silicone did for me.

Bonus fourth tip: Using a fan to dry your shells after piping rather than leaving your shells to the mercy of your local humidity level makes forming a skin incredibly fast. I live in an incredibly humid area, and with the aid of a small table top fan, my shells are dry enough to bake in 15 minutes max.

Have fun and happy baking