Blueberry Crumble Questions

Can I use frozen blueberries instead of fresh ones?

Yes, but add them to the saucepan still frozen so they don't turn mushy while thawing. Frozen berries release more liquid, so let the mixture bubble a little longer after stirring in the cornstarch until it visibly thickens. A too-runny filling will soak into the dough base and make it soggy.

What can I use instead of the ground and chopped almonds?

Ground hazelnuts work as a one-to-one swap for the 30 g of ground almonds in the dough, and chopped hazelnuts or pistachios can replace the 20 g in the crumble. If you need a nut-free version, replace the ground almonds with the same weight of flour and simply leave the chopped nuts out of the crumble. The crumble will be a bit less crunchy, so bake it to a slightly deeper golden colour.

How do I store the tartlets and how long do they stay good?

Keep them in a loosely covered container at room temperature rather than in an airtight box, since trapped moisture from the berry filling softens the crumble. They are best on the day of baking and still good the next day. To refresh them, warm them in the oven for a few minutes and dust with powdered sugar only just before serving, because it dissolves on contact with the fruit.

Can I prepare parts of the recipe in advance?

Yes, all three components keep well separately. The dough can be wrapped and chilled instead of just resting briefly, the cooked blueberry filling can be made ahead and cooled completely, and the crumble can be rubbed together and kept cold until you need it. Let the dough sit at room temperature for a few minutes before rolling so it doesn't crack.

Why did my tartlets leak or stick in the molds?

The recipe deliberately says not to press the dough up the edges, so the filling sits on a flat base - spoon it on sparingly and keep it in the middle, or it will run over the side and caramelise between dough and mold. Grease the molds and let the tartlets cool completely before unmolding, since warm butter-rich dough is still fragile and tears easily. If the filling was too thin because the cornstarch never came to a boil, it will seep out no matter how carefully you fill them.