Preheat the oven to 200°C / gas mark 6. Put the hulled strawberries into your pie dish (I use a round one) and sprinkle over them the sugar, almonds and vanilla extract. Give the dish a good shake or two to mix the ingredients.
Now for the crumble topping: Put the flour and baking powder in a mixing bowl and rub in the cold, diced butter between thumb and fingers (or in a freestanding mixer).
When you've finished, it should resemble rough, pale oatmeal. Stir in the flaked almonds and sugar with a fork.
Tip this over the strawberry mixture, covering the strawberries in an even layer and giving a bit of a press in at the edges of the dish. Set the dish on a baking sheet and bake in the oven for 30 minutes, by which time the crumble topping will have darkened to a pale gold and some pink-red juices will be seeping and bubbling out at the edges.
Leave to stand for ten minutes before serving, and be sure to put a jug of chilled double cream on the table alongside.
Make ahead note:
The crumble can be assembled one day ahead. Cover with clingfilm and store in fridge until needed. Bake as directed in recipe, but allowing extra 5-10 minutes' cooking time and check crumble is piping hot in the centre.
Crumble topping can be made and frozen in resealable plastic bags, for up to three months. Sprinkle topping direct from freezer over fruit, breaking up large lumps with your hands. The assembled but unbaked crumble can be frozen, wrapped in a double layer of clingfilm and a layer of foil, for up to three months. Defrost for 24 hours in fridge and bake as above.
Recipe from Nigella: Kitchen by Nigella Lawson (published by Chatto & Windus).