Feb 04, 2013 Turnip & Mustard Gratin Ingredients 500g turnips 250ml double cream 3 tbsp crème fraîche 2-3 tbsp Dijon mustard 100g Gruyère , grated Method Heat the oven to 180C/fan 160C/gas 4. Peel and slice the turnip thinly. soak the pieces in some cold water for 5 minutes, then drain the slices and drop into boiling water for 2-3 minutes to blanch them. Bring the cream to the boil. add the crème fraîche and dijon mustard. Mix the cream mixture with the turnip, pour the whole lot into a buttered dish and sprinkle with grated gruyère. Tap the dish so it all packs down and cook for about 40-50 minutes, or until golden, bubbling and tender. Source: BBC Good Food