I had most of a pot of creme fraiche leftover about to go out of date and I was looking for a recipe to use it so it didn't go to waste, a bit of googling produced this recipe. It isn't as good as a gratin recipe with cream but it was edible and used up ingredients that I already had in the cupboards.
Potato and Leek Gratin (from Vermont Creamery)
(Serves a large number of people)
3 leeks, sliced in half lengthwise, cleaned, and chopped
2 cloves garlic, minced
salt and pepper
1 tbsp fresh thyme, chopped
375ml whole milk
225g crème fraîche
1.8kg potatoes, peeled and sliced thin
100g cheddar or gruyère, grated
Preheat the oven to 200°C. Melt the butter in a large frying pan over a medium heat.
Add the leeks and garlic, stirring occasionally to allow the leeks to soften and caramelise a little. Add the salt, pepper, thyme, and milk, and allow to come to a boil, stirring frequently.
Lower the heat and stir in the crème fraîche. Add the sliced potatoes and allow to simmer for a few mins. Make sure to gently stir the potatoes so they are all coated. Butter a large gratin or casserole dish, and pour the potatoes and sauce into it. Sprinkle with the cheese, and bake for 1 hour, until the potatoes are soft.