Joulukakku

After 25-30 minutes at 175 °C / 350 °F the surface should be lightly golden and the sugar-almond topping just starting to color. Because the batter is thin on a 27 × 17 cm tray, it bakes fast - start checking at 25 minutes. A skewer inserted in the center should come out with no wet batter clinging to it.

Ground hazelnuts work well and give a darker, more roasted flavor; use the same 50 g. You can also swap in the same weight of flour, but the bread will be drier and less tender, since the almonds contribute fat and moisture. Avoid almond flour that is much coarser than "finely ground," as it makes the batter grainy.

Let it cool completely on the tray or a rack first, then cut it into pieces and keep it in an airtight tin at room temperature. Storing it warm traps steam and softens the crisp sugar-almond topping. The recipe notes it tastes especially good after resting, so a day or two in the tin only helps; it also freezes well once fully cooled.

The batter should not sit around - the whipped egg whites are what lift it, and they deflate quickly, so spread it on the tray and bake right away. What you can do ahead is measure the flour, ground almonds, salt, and cinnamon into one bowl and the sugar and sliced almonds for sprinkling into another. Better still, bake the whole tray a day early, since the flavor improves as it rests.

Folding the stiff egg whites in too roughly, or stirring them until the batter looks smooth - that knocks out the air and gives a flat, dense bread. Fold gently with a spatula and stop while a few white streaks are still visible. The second common slip is butter that is not truly soft: cold butter will not beat pale and creamy with the sugar, and the batter stays lumpy.