Preheat the oven to 200ºC/400ºF/gas mark 6

Remove the cardamom seeds from their husks and grind finely with a pestle & mortar

Slice the rhubarb into 2½cm/1inch slices

Peel, core & chop the apple into 1cm/⅓ cubes

Put the rhubarb, apple, half the ground cardamom and 2tbs of the sugar into a medium-sized bowl and mix until the sugar coats the fruit evenly

Decant the mixture into a 30cm x 15cm oven-proof dish

In a medium-sized bowl, add the flour, oats, sugar, chopped almonds, butter and remainder of the cardamom. Rub in the ingredients with your fingers until they resemble coarse, lumpy breadcrumbs

Cover the sugared fruit evenly with the crumble mixture

Cook for 20-30 minutes until the top has begun to brown and fruity syrup is bubbling up

Allow to cool slightly and serve with custard or vanilla ice cream