Stir the boiling water, vanilla pod, and 3 dessertspoons caster sugar together in a saucepan over a low heat to make a syrup.
Pour half the liquid with the vanilla pod into a separate pan and the rhubarb and cook until the rhubarb softens.
Pour the other half over the strawberries and blitz with a handheld blender to make a puree. Pass through a sieve into a bowl to remove any seeds.
Put the walnuts in a food processor, add the melted butter and a little caster sugar and blitz briefly till the nuts are in small pieces. Transfer to a pan and grill for a couple of minutes to toast.
Place the rhubarb in the centre of the plate, spoon around the strawberry sauce and sprinkle the walnut crisp onto the top of the rhubarb. Serve with a spoonful of clotted cream.
