• 2½ cups all-purpose flour
• 1 cup rolled oats
• 1 cup packed brown sugar
• ½ tsp baking powder
• ½ tsp salt
• 1 cup unsalted butter, melted
• 3 cups frozen diced strawberries
• ⅓ cup sugar
• 2 tbsp cornstarch
• 1 tbsp lemon juice

1. Heat the oven to 350°F (175°C) and line a 9x13-inch pan with parchment, leaving an overhang.
2. Mix the flour, oats, brown sugar, baking powder and salt. Stir in the melted butter until crumbly.
3. Press two-thirds of the mixture firmly into the pan and bake for 12 minutes.
4. Meanwhile, toss the frozen strawberries with sugar, cornstarch and lemon juice.
5. Spread the strawberries over the warm base, then scatter the remaining crumble on top.
6. Bake for 35-40 minutes, until the top is golden and the filling bubbles at the edges.
7. Cool completely in the pan, then lift out and cut into 16 bars.

Baking with frozen fruit: diced strawberries spread evenly and bake into a jammy layer without any chopping. Keep them frozen until you toss them with the cornstarch so the filling sets firm enough to slice.