Why are my macarons hollow inside?

The shell looks right, the foot is there, and then you bite into a crisp dome with nothing underneath. What has happened is that the batter inflated rapidly — the shell set at the top, the internal structure could not support itself, and everything collapsed down onto the base leaving a void. The fix is counter-intuitive to anyone who has spent weeks trying to get *more* rise: you want less violent expansion and a longer, gentler bake that sets the interior as well as the surface.

What you'll need

• An oven thermometer
• A stand mixer or hand mixer (optional)

Step by step

1. Stop the meringue a little earlier.Stiff peaks with a glossy surface. Meringue whipped until it is dry, matte and starting to look grainy carries more air than the batter can support and collapses in the oven.
2. Fold a few strokes further.Under-mixed batter holds large air pockets that expand rapidly and leave voids. If your shells are hollow and slightly lumpy, the macaronage stopped too early.
3. Drop the oven temperature and extend the bake.10°C lower and three to five minutes longer. A hot oven inflates the shell before the interior has set, which is precisely how a hollow forms. This is the highest-value change.
4. Check the tray and the shelf.Excessive base heat drives the batter upward. A doubled tray, an insulated sheet, or moving up a shelf all reduce it.
5. Bang the tray properly before resting.Large trapped bubbles become cavities. Several firm drops onto the worktop, then pop what rises with a cocktail stick.
6. Test doneness by the wiggle, not the clock.Push a shell gently sideways. If the top moves independently of the foot, the inside has not set — give it another minute or two. A shell that moves as one piece is baked.
7. Mature the filled macarons.Filled shells left in the fridge for 24 hours absorb moisture from the filling, and a slight hollow largely disappears. This is standard practice and it fixes minor cases entirely.

Tips

• Italian meringue produces markedly fewer hollows than French, because the hot syrup partially cooks and stabilises the whites.
• Adding a small amount of the almond mixture back if the batter has gone runny does not work. Start again rather than trying to thicken over-mixed batter.
• A slightly under-filled piping — smaller shells — sets through more reliably than large ones and is a good way to diagnose while you adjust the oven.
• Hollow macarons still taste correct. Fill them generously and nobody will comment.

Common mistakes

• Resting the shells longer to fix hollows — Resting controls the skin and therefore the feet and cracks. It has almost no effect on hollowing, which is an internal structure problem.
• Adding more almond flour to thicken a runny batter — The ratio is what makes the shell work. Extra almond gives a coarse, oily shell that fails differently.

If it doesn't work