For the crumble topping
- STEP 1
Tip 500g thumb-length chunks of rhubarb into a saucepan with 100g golden caster sugar and 3 tbsp port, if using.
- STEP 2
Cover and simmer on a very low heat for 15 mins, adding more sugar if you want. When soft (but still holding its shape) and sweet enough, pour the rhubarb into a medium baking dish.
- STEP 3
Heat oven to 200C/180C fan/gas 6.
- STEP 4
To make the topping, rub 140g self-raising flour and 85g chilled butter together with your fingers until you have a soft, crumbly topping.
- STEP 5
Now add 50g light brown muscovado sugar and 50g chopped walnuts, if using. Mix together with your hands.
- STEP 6
Scatter the topping over the rhubarb and bake for 30 mins or until golden brown on top.
- STEP 7
Serve piping hot with a big jug of thick vanilla custard. Refer to the tip for a recipe.