100g mixed nuts, such as walnuts, brazil nuts, almonds and hazelnuts, roughly chopped (you can buy these as a mixed pack)
1 tsp ground cinnamon
250g dark muscovado sugar
1 large egg
225g plain flour
1 tsp bicarbonate of soda
2 x 142ml cartons soured cream
300g rhubarb, cut into 1cm pieces
Preheat the oven to 180C/gas 4/fan 160C. If baking to cut into squares, line a 33 x 23 x 5cm baking tin with non-stick baking parchment. If serving as a pudding simply grease a similar-sized ovenproof dish with a little butter.
Melt about 15g/1a„2oz of the butter and stir into the caster sugar, nuts and cinnamon in a bowl. Set aside.
Cream together the rest of the butter with the muscovado sugar and egg. When smooth and creamy, stir in the flour, bicarbonate of soda, 1a„2 tsp salt and the soured cream. Lastly, stir in the rhubarb.
Pour the rhubarb mixture into the prepared tin and sprinkle with the sugar and nut topping. Bake for 30-35 minutes or until a skewer inserted in the centre comes out clean. Serve immediately as a pudding, or leave to cool and cut into squares. Keeps for 4-5 days in an airtight tin.