Jordbær-yoghurtbarer med smuldredej

Fresh or frozen berries release much more water than the 150 g of jam, which would leave the filling loose and soak the pre-baked crust. If you want to use them, cook them down with a little sugar first until thick and jammy, then cool completely before folding into the yogurt. The filling relies on the jam being thick, since only 1 tbsp of cornstarch and one egg are doing the setting.

Greek yogurt works well and gives an even firmer, creamier set than plain yogurt, since it carries less liquid. Thick plant-based yogurts (soy or coconut) also work, but avoid thin drinking-style yogurts, which will make the filling runny. Whatever you use, whisk it smooth with the egg and cornstarch so no lumps stay behind.

After 30-35 minutes the crumble topping should be golden and the center should still jiggle slightly when you nudge the pan - that wobble sets as it cools. If the center is still liquid and sloshes rather than wobbles, give it a few more minutes. Baking until the center is completely firm will overcook the egg and make the filling grainy.

Because the filling contains yogurt and egg, keep the bars covered in the fridge rather than at room temperature. They're a good make-ahead bake: the flavors settle and the filling firms up further after chilling, which also makes slicing cleaner. You can also press the crumble mixture into the pan a day ahead and keep it cold until you pre-bake.

The two big ones are using butter that isn't cold enough - it smears instead of rubbing into crumbs, so you lose the crumbly texture - and slicing while still warm, which drags the filling and ruins clean edges. Skipping the 12-15 minute pre-bake is another: the crust needs that head start or it turns soggy under the wet filling. Also stir the jam smooth before folding it in, or you'll get dense streaks instead of an even or nicely marbled layer.