# What You'll Need:
→ Crumble base & topping
01 - 1 1/2 cups all-purpose flour
02 - 1 1/2 cups rolled oats
03 - 3/4 cup granulated sugar
04 - 1/2 cup light brown sugar, packed
05 - 1/2 teaspoon fine salt
06 - 1 teaspoon ground cinnamon
07 - 1 cup unsalted butter, melted
→ Strawberry–rhubarb filling
08 - 2 cups fresh strawberries, hulled and diced
09 - 2 cups fresh rhubarb, diced
10 - 2/3 cup granulated sugar
11 - 2 tablespoons cornstarch
12 - 2 teaspoons vanilla extract
13 - 2 teaspoons lemon juice
# Step-by-Step Guide:
01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper, leaving a 2-inch overhang on two sides for easy removal; set pan aside.
02 - In a large bowl, whisk together the flour, rolled oats, granulated sugar, brown sugar, salt, and cinnamon until evenly distributed.
03 - Pour the melted butter over the dry mixture and stir with a spatula until cohesive, coarse crumbs form; reserve 1 1/2 cups of the crumb mixture for the topping.
04 - Firmly press the remaining crumb mixture into the bottom of the prepared pan to create an even base layer about 1/2 inch thick.
05 - In a separate bowl, toss the diced strawberries and rhubarb with the granulated sugar, cornstarch, vanilla, and lemon juice until the fruit is evenly coated and the cornstarch is incorporated.
06 - Spread the fruit mixture in an even layer over the pressed base. Scatter the reserved crumb mixture uniformly over the fruit to cover the surface.
07 - Bake on the middle rack for 40 to 45 minutes, or until the topping is golden brown and the filling is bubbling at the center.
08 - Remove from oven and cool completely in the pan on a wire rack. Use the parchment overhang to lift the slab from the pan and cut into 12 bars once fully cooled.
