Testing - Célériac au gratin

http://www.jamieoliver.com/recipes/vegetables-recipes/celeriac-gratin/#bVG0xq6RyMcu2h3u.99

1 - This was very nice, but I can't quite remember how I prepared it. It's staying in the testing phase!
1.0 - Try it with gruyère.

2 lbs potatoes, peeled and sliced into 1cm slices
1 large celeriac, peeled and sliced into 1cm slices
1 onion, peeled and finely sliced
sea salt
freshly ground black pepper
2 cloves garlic, peeled and finely chopped
3 oz Cheddar cheese, grated Try with Gruyère cheese
2 1/2 cups crème fraîche
1 small bunch fresh flat-leaf parsley, leaves picked, stalks roughly chopped

1. Preheat your oven to 400F.
2. Place the potatoes, celeriac and onion in an earthenware-type baking dish. Season generously.
3. Add the garlic, ¾ of the cheese, the cream and the parsley stalks.
4. With a spoon, move everything around to mix all the flavours.
5. Sprinkle over the extra cheese, and bake in the preheated oven for 50 minutes, or until tender and golden.
6. Sprinkle over the parsley leaves.