Step 1

Preheat the oven to 400 degrees F. Grate all three cheeses. (Unless using pre-grated.)

Step 2

Use a vegetable peeler to peel the sweet potatoes, then slice them about ¼ inch thick. If your potatoes are large, cut the slices into half moons or quarters to ensure quick cooking. Put the sweet potato slices in a 9" x 13" casserole dish or similarly sized gratin dish.

Step 3

Chop the chipotle chiles finely.

Step 4

Place a medium skillet over medium heat. Add the heavy cream, salt, parmesan, chipotle chiles and adobo sauce. Stir occasionally and heat to the point that it just barely begins to simmer. Don't scorch the cream.

Step 5

Pour the creamy chipotle sauce over the sweet potatoes, cover tightly with foil, and place in the oven. Bake for 30-40 minutes until the potatoes in the center of the dish are fork tender. WARNING: When you remove the foil to check the potatoes, be VERY careful! Hot steam will have built up underneath the foil and you could burn yourself. See note below.

Step 6

When the potatoes are fork tender, remove the foil and place the casserole dish back in the oven for about 5 minutes to allow the sauce to thicken. Remove from oven and set the broiler to high.

Step 7

Top the sweet potatoes with the monterey jack and gruyére cheeses and place under the broiler until the cheeses are melted and bubbling on top. Remove from oven and allow to stand 10 minutes before serving.