I recently made Marian Bull's Blueberry Schlumpf. Delicious; love how simple and pure it is and how the blueberries really shine. The only change I made was to add a little lemon juice and lemon zest to the blueberries to help brighten their flavor. Anyway, it will now be a summer staple and probably equally good with other seasonal fruits. My question is the streusel topping. Is there a secret to keeping it firm and crunchy, like right out of the oven and cooled? Making it for a household of 1 or 2, it lasts for a few days, during which the streusel topping gets a bit soggy and slumps--not any less flavorful, but the textural difference is not as good, and the presentation would suffer, as well. On the counter, I just covered the pan with aluminum foil. Anyway, didn't know if there was a trick that I had missed along the way. Thank you.