Beetroot Rhubarb Potato Gratin

|A recipe from Anna Jones that combines comfort of potatoes and cream with the tart rhubarb and earthy beetroot. A pleasantly surprising trio for a gratin.|beetroot potatoes rhubarb|butter for greasing1 kg potatoes preferably waxy ones such as Desiree or Charlotte500 g cooked beetroot peeled300 ml weak vegetable stock300 ml double cream150 ml sour cream2 bay leaves1/2 teaspoon black peppercorns200 g rhubarb thinly sliced|Preheat the oven to 200 C / 180 C fan / gas 6. Butter a large gratin dishPeel the potatoes and slice them very finely - a mandoline or the fine slicer attachment on a food processor is the easiest way to do this. Cut the beetroot into fine slices as well.Put the stock and both the creams into a large saucepan along with the bay leaves and the peppercorns. Bring the liquid to just under the boil then take off the heat and leave to sit for 30 minutes or so. Remove the bay leaves leaving the peppercorns and bring the liquid to just below a simmer. Add the sliced potatoes and cook gently for 5 minutes.Remove from the ehad season really well with salt and pepper and spoon half the potoates into the gratin dish. Put half the beetroot and rhubarb on top seasoning as you go then top with the rest of the potatoes and their cream followed by the rest of the beetroot.Sprinkle the top with extra freshly ground pepper if desired. Bake for 1 hour or until the vegetables are completely tender. Cover the top with foil after about 45 minutes if it looks like it is becoming too brown.|10.00 minutes|6|Anna Jones