Potato, Onion and Garlic Gratin

3Tbsp butter
1 large onion cut into thin rings
2-4 cloves of garlic finely chopped
2lbs of waxy potatoes very finely sliced
1/2 tsp each of dried rosemary and thyme
2 cups of boiling vegetable stock (aprox)
sea salt and fresh ground pepper
sharp cheddar cheese, or gruyere cheese grated (opt)

Lightly grease the inside of the crock pot with the melted butter. Sppon a layer of oinion on the bottom, add a bit of garlic and seasonings. Arrange an overlapping layer of potatoes over the onions. Repeat with onions, spices and then finish with the last of the potatoes. Pour just enough of the stock to just cover the potatoes . Cover and cook on low 8-10 hours or on high 4-5 until the potatoes are tender. If too liquidly just remove cover and set on high for 30 mins to allow for evaporation. It should not be if you used just a scant amount of liquid to just cover the potatoes.
To brown them slightly you can put the ceramic dish under the broiler for 3-4 mins. Alternatives are to add grated cheese and broil till bubbly.
Another alternative is to add 1 cup of soft goat cheese on top of the gratin before the end of cooking time in the crockpot.