Wash the blueberries and gently pat them dry. Preheat the oven to 375°F and butter the bottom and sides of a 1-1/2 quart baking dish.
Place the blueberries in a large bowl, sprinkle with the cornstarch and cinnamon and toss to coat. Add the lemon juice, mix well and transfer the mixture to the prepared baking dish (see recipe notes). Set aside.
Place the cereal in a food storage bag and using a rolling pin, crush the flakes into coarse crumbs. You should end up with 1/3 to 1/2 cup.
Place the cereal in a bowl and add the flour, sugar and cinnamon. Mix well. Add the melted butter, combine thoroughly, then taste and add more sugar if desired.
Using your fingers, crumble about half of the cereal mixture over the blueberries and combine gently.
Crumble the remainder of the topping over the berries, cover and bake until the berries are tender, 30 to 35 minutes.
Uncover and return to the oven until the topping is crisp and golden brown and the berries are bubbly, 8 to 12 minutes more.
Allow the crisp to cool for 30 to 40 minutes, then spoon into individual serving dishes. Top with fresh whipped cream or vanilla ice cream if desired.
Tips for Making This Recipe
Taste your blueberries and if you find them to be especially tart, you may want to add 1 tablespoon of sugar along with the cornstarch and cinnamon.