1In a big bowl, toss the strawberries and plums. In a small bowl, stir together the sugar and cornstarch (this will get rid of any lumps); shake over the fruit and toss to coat. Spread into a baking dish - I like quiche dishes, which allow for maximum surface area.
2Blitz together the crumble ingredients in a food processor until well combined. Scatter over the fruit, squeezing as you go to make larger clumps.
3 Bake at 350F for half an hour, or until bubbly around the edges and golden on top.