Preheat oven to 375°F (190°C).
In a bowl, combine strawberries, raspberries, sugar, cornstarch, cardamom, lemon juice, and vanilla extract. Toss gently and pour into a greased baking dish.
In another bowl, whisk flour, sugar, baking powder, salt, and cardamom.
Cut in butter using a pastry cutter or fork until the mixture resembles coarse crumbs.
Add heavy cream and stir until a soft dough forms.
Drop spoonfuls of biscuit dough over the fruit filling, leaving some gaps for steam to escape.
Brush the tops with cream and sprinkle with coarse sugar.
Bake for 35–40 minutes, until the biscuits are golden brown and the fruit is bubbling.
Cool slightly before serving. Serve warm with ice cream or whipped cream.