Preheat your oven to 350°F/175°C. Butter a 9-inch deep dish pie plate.
Whisk together the flour, cinnamon, salt, oats and light brown sugar together in a large jug or medium bowl. Add in your cubed butter and use your fingers or a pastry cutter to rub the butter until it is very crumbly and everything is moistened. Place in the fridge while you prepare the filling
½ cup light brown sugar, 1 cup rolled oats, ½ cup all purpose flour, 1 stick unsalted butter, 1 teaspoon ground cinnamon, pinch salt, ½ teaspoon ground cardamom
In a large bowl, mix all of your filling ingredients together and toss.
2 ½ cups blackberries, 2 cups granny smith apples, 3 tablespoon cornstarch, ¼ cup white sugar, ¼ teaspoon kosher salt, 1 ½ teaspoon vanilla extract
Spread the filling out into an even layer of your dish. Make sure there are no gaps! Sprinkle over your topping mixture evenly.
Bake for 40-45 minutes. If it gets too brown, place some foil on top. The juices should be bubbling and the streusel top should be golden.
Allow it to cool for at least 5 minutes before serving.
Notes
My recipes have been developed and tested in metric grams. I highly recommend using a weighing scale and measuring out your ingredients the metric way. Just click on ‘Metric’ above the ingredient list.Salt: If you don’t have kosher salt, halve the amount of salt called for in the recipe. 1 teaspoon kosher salt = ½ teaspoon fine salt. I am using Diamond Crystal Kosher Salt, not Morton Salt which is far too salty for this!Deep Dish: you can use a deep dish pie plate if you prefer, I recommend adding another cup of diced apples if you do this. Storage: Keep the blackberry and apple crumble covered and in the fridge for up to 5 days. I recommend warming it up before serving!