Preheat your oven to 375°F (190°C). Butter a 9x13-inch casserole dish generously.

In a large mixing bowl, combine your fresh berries with ½ cup sugar, cornstarch, lemon juice, and vanilla extract. Toss gently and let sit for about 10 minutes.

Pour the berry mixture into your prepared casserole dish and spread evenly.

In another bowl, whisk together flour, ⅔ cup sugar, baking powder, and salt.

Add cold butter pieces to the flour mixture and work into coarse crumbs.

Pour in cold milk and stir gently until just combined.

Drop spoonfuls of the topping over the berry mixture.

Sprinkle the top with an extra tablespoon of sugar.

Bake for 45-50 minutes until the topping is golden brown and berry juices bubble.

Let cool for at least 15 minutes before serving.