Blueberry Crumble

1. Heat the oven. Preheat to 375°F. Lightly butter an 8x8-inch baking dish. If your dish is very full, set it on a baking sheet to catch any bubbly berry drips.
2. Mix the blueberry filling. In a large bowl, combine blueberries, granulated sugar, lemon juice, lemon zest, cornstarch, cinnamon (if using), and salt. Toss until the berries look evenly coated, then toss in the vanilla. Pour into the prepared baking dish and spread into an even layer.
   
3. Make the crumble topping. In a medium bowl, whisk together flour, oats, brown sugar, granulated sugar, baking powder, cinnamon, and salt. Add the cold cubed butter and cut it in with a pastry cutter or fork until you get a mix of sandy crumbs and pea-sized clumps. Those buttery clumps are what become crisp little nuggets on top.
   
4. Top it. Sprinkle the crumble evenly over the blueberries. Do not pack it down. Keep it fluffy so the heat can crisp it up.
5. Bake. Bake for 35 to 45 minutes, until the topping is deep golden brown and the blueberry filling is bubbling around the edges and in a few spots near the center. If using frozen berries, bake toward the longer end and look for bubbling in the center, not just the edges.
   
6. Rest, then serve. Let cool for 15 to 20 minutes so the filling thickens. Serve warm. Ice cream is highly encouraged and so is tasting the crispy edges first.

Practical Tips and Variations

• For extra crisp: Add 2 tablespoons chopped pecans or walnuts to the topping.
• Make it a mixed berry crumble: Use 2 cups blueberries plus 2 cups raspberries or blackberries. If the berries are very juicy, add an extra 1 to 2 teaspoons cornstarch.
• Dial up the cozy: Add a pinch of nutmeg to the topping or a tiny pinch of cardamom to the filling.
• Less sweet: Reduce sugar in the filling to 1/3 cup if your berries are super ripe and sweet.
• Serving ideas: Vanilla ice cream, whipped cream, or plain Greek yogurt with a drizzle of honey for a breakfast-dessert situation.