I make a big batch of crumble topping and freeze what I don't use.
250g butter, cold and cut into cubes
600g self-raising flour
250g Caster sugar
100g Soft brown sugar
100g chopped hazelnuts
100g chopped almonds
2 tsp ground cinnamon
2 tsp ground ginger
(the nuts and spices can be omitted if you don't like them)
I make it by hand but if you have a processor then it's much easier. Just put the butter,flour, sugars and spices if using them into the processor. Whizz until it resembles breadcrumbs. Stir the nuts through the mixture if using them.
If making by hand, rub the flour into the butter using your fingertips until it resembles breadcrumbs. Stir in the sugars, spices and nuts.