Now this may be a little bit of work but most of the real work happens in the oven. While that's going on, you can clean all the pans you used, which I must admit there are quite a few. It is quite colorful looking - rather than that pale looking regular potato gratin. Two-Potato Gratin (Adapted from Cooking Light ) 2 medium baking potato, peeled and sliced 1/4" thick 2 medium sweet potato, peeled and sliced 1/4" thick 2 quarts chicken stock 2 T oil 3 green onions, sliced 2 garlic cloves, crushed 1 T fresh thyme 3 T flour 1 1/2 c milk 1 c chicken stock (reserved from potato liquid) salt/pepper 3 oz Gruyere cheese, grated 1 oz (1/4 c) Parmesan Cheese Place potatoes in a stockpot with chicken stock. Bring to a boil and cook for 4 minutes. Meanwhile in a saucepan heat oil and green onions. Saute until softened, add garlic and thyme. Cook until fragrant. Whisk in flour and cook for about 3 minutes. Gradually add milk; whisking constantly. Remove potat...