for my crumble topping:
200 g (1 3/4 cup) flour
50 g (1/4 cup) caster sugar
50 g (1/4 cup) light brown sugar
25 g (1/4 cup) porridge oats (optional)
1/4 teaspoon fine sea salt
100 g (1/2 cup) butter, melted
Crushed walnuts added in
Preheat the oven to 190°C (375°F).
To make the topping, combine the flour, caster sugar and brown sugar, oats and salt in a bowl. Stir in the melted butter, then squeeze the topping with your hands to make small clumps. Put the topping in the fridge while you prepare the filling.
Place the chopped rhubarb sugar, corn flour and lemon zest in a large bowl and stir together well. Add in the walnut halves and stir gently.
Place the filling in a large ovenproof dish or individual dishes. Sprinkle the topping over the fruit, making sure it’s evenly distributed. Bake for 45 to 60 minutes, until the topping is golden and the filling is bubbling up. Allow to cool for 15 or 20 minutes before serving with cream, custard or ice cream. A crumble is best eaten straightaway, but any leftovers make an excellent breakfast the next day