Yukon Gold Potatoes with Sweet Onion au Gratin

YUKON GOLD POTATOES WITH SWEET ONION AU GRATIN
2 T. butter
2 large Vidalia onions, thinly sliced
Salt and black pepper
1 t. ground thyme
1 bay leaf
2 lbs. baby Yukon gold potatoes
½ to 2/3 c. heavy cream
¾ c. freshly grated parmesan cheese
½ lb. shredded gruyere cheese

1. Heat a small skillet and add butter.
2. Add onions and season with thyme, bay leaf, salt and pepper.
3. Cook until tender. Season to taste again. Discard bay leaf.
4. Place potatoes in cold water seasoned with salt. Bring to boil and cook until tender.
5. Drain and return potatoes to pot.
6. Mash potatoes with cream and parmesan cheese. Season to taste.
7. Preheat broiler.
8. Arrange the potatoes into individual au gratin dishes or 1 shallow casserole dish.
9. Top potatoes with onions and gruyere cheese.
10. Place the dishes or casserole dish on a baking sheet and place under broiler until bubbly, about 2 minutes. Remove from oven and serve.
    *If you do not want to mash, you can slice the cooked potatoes, as well.