For the filling:
300 grams rhubarb stalks, trimmed and sliced 1/2-inch thick
200 grams strawberries, hulled and quartered
90 grams granulated sugar
1 + 1/2 tablespoons cornstarch
1 teaspoon vanilla extract
For the topping:
124 grams all-purpose flour
68 grams light brown sugar
25 grams granulated sugar
1/8 teaspoon kosher salt
6 tablespoons unsalted butter, cut into 1/2-inch cubes
70 grams old fashioned rolled oats
Prep time: 20 mins
Bake time: 50 mins
Preheat the oven to 350 F (176 C)
For the filling:
In a large bowl, combine the rhubarb, strawberries, sugar, cornstarch, and vanilla. Stir until the fruit is evenly coated with the sugar mixture, and the sugar mixture is no longer white.
Transfer the fruit mixture to a 8-inch baking dish (no need to butter it) and set aside while you prepare the topping.
For the topping:
In the bowl of a food processor, combine the flour, brown sugar, granulated sugar and salt. Process until well combined, about 30 seconds. Add the cold butter and pulse until the mixture resembles coarse crumbs, with a few pea-sized clumps of butter within. Transfer to a medium bowl and stir in the oats.
Spoon the topping evenly over the fruit without packing down. Bake for 45-55 minutes, until the fruit is bubbling around the edges and the topping is golden brown. Cool for 20 minutes before serving.