Preheat oven to 375°F; lightly grease a 9x13-inch dish.
Gently toss strawberries, rhubarb, 1 cup sugar, cornstarch, and vanilla in a large bowl. Stand 10 minutes; pour into dish.
Whisk flour, 1/3 cup sugar, baking powder, and salt in another bowl; cut in cold butter with pastry cutter or fork to coarse crumbs.
Stir in cream just until soft dough forms; do not overmix.
Drop dough spoonfuls over fruit, leaving steam gaps. Sprinkle with coarse sugar.
Bake 40-45 minutes until topping is golden brown and fruit bubbles.
Cool 15 minutes; serve warm with ice cream or whipped cream.