For the Filling:

• 4 cups fresh blackberries (or frozen, thawed and drained)
• ½ cup granulated sugar
• 2 tablespoons cornstarch
• 1 tablespoon lemon juice
• 1 teaspoon vanilla extract
• ½ teaspoon cinnamon (optional)

For the Crisp Topping:

• 1 cup old-fashioned rolled oats
• ¾ cup all-purpose flour
• ½ cup brown sugar, packed
• ½ teaspoon baking powder
• ½ teaspoon salt
• ½ cup unsalted butter, melted
• ½ teaspoon cinnamon (optional)

Instructions

1. Prepare the Filling:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Mix the Filling: In a large bowl, combine the blackberries, granulated sugar, cornstarch, lemon juice, vanilla extract, and cinnamon (if using). Gently toss to coat the blackberries evenly.
3. Transfer to Baking Dish: Pour the blackberry mixture into a greased 9×9-inch (or similar size) baking dish, spreading it out evenly.

2. Make the Crisp Topping:

1. Combine Dry Ingredients: In a separate bowl, mix together the rolled oats, flour, brown sugar, baking powder, salt, and cinnamon (if using).
2. Add Butter: Pour the melted butter over the dry ingredients and stir until the mixture is crumbly and well combined.

3. Assemble and Bake:

1. Top the Filling: Evenly distribute the crisp topping over the blackberry filling in the baking dish.
2. Bake: Bake in the preheated oven for about 30-35 minutes, or until the topping is golden brown and the blackberry filling is bubbling.

4. Serve:

1. Cool Slightly: Let the blackberry crisp cool for about 10-15 minutes before serving.
2. Enjoy: Serve warm, optionally with a scoop of vanilla ice cream or whipped cream on top!