Celeriac and Potato Bake

|Celeriac and Potato Bake|potatoes|1 celeriac peeled and cubedjuice from one lemon50g butter100 ml creme fraichesalt and pepper3 potatoes peeled and cut into 5mm slices25g parmesan freshly grated|Put the cubes of celeriac in a pan of salted boiling water with the lemon juice. Cook for 15 - 20 minutes until the celeriac is tender.Drain the celeriac well and place in a food processor or the bowl of a hand blender. Add the butter and the creme fraiche.Puree until the celeriac is smooth. Season with a little salt and pepper.Preheat the oven to 220C/425F/Gas Mark 7. Put the potatoes in a pan of boiling salted water for about 4 - 5 minutes until they are just begining to soften. Don't allow them to overcook or become mushy. Carefully drain without breaking the slices.In a round or oval ovenproof dish arrange a layer of potato slices. Then add a third of your celeriac puree on top spreading it evenly over the potato. Add another layer of potato slices then a layer of puree and so on until you have used all your potato. Finish with a layer of puree.Sprinkle the parmesan cheese on top. Cook in the oven for 15 minutes until the top is a crispy golden brown.|30.00 minutes|1|