Based on Nigel’s Oat plum crumble from The Guardian (qtys for 4 – or 2 with seconds)
350g plums, stoned and quartered
2 tbsp caster sugar
a small knob of butter
50g plain flour
50g ground almonds (can just use 100g flour if you prefer)
35g light brown or demerara sugar
40g rolled oats
Heat oven to 200ºC. To make the crumble, rub the butter into the flour, then stir in almonds, sugar and oats.
Put the cut fruit into the medium white pie dish with sugar, butter and 2 tbsp water. Tip the crumble on top and bake for 30-35 minutes until the topping is crisp and golden and the fruit is soft. Serve hot, with cream or custard.
For apple crumble, peel, core and slice 750g apples (for 6 people) and then cook them briefly in a saucepan (2 mins) with 1 tbsp butter , 3-4 tbsp sugar and a squeeze of orange juice or 2 tbsp water before tipping them into the dish. Crumble as above, double quantity, using all flour. Can add ½ tsp cinnamon, and chopped walnuts are a nice addition to the crumble.
Rhubarb crumble: trim 1 kg rhubarb, pull off any stringy bits, cut into 5 cm pieces and put into dish with zest of an orange and a little orange juice (and a tsp of ground ginger if you like). Nigella uses 120g self-raising flour, 90g butter and 6 tbsp sugar (50/50 light muscovado and caster, method as above) to top her rhubarb crumble, though I really like substituting say 40g of the flour with ground almonds.