Sweet Potato Gratin

I made this recipe recently for a potluck at a friends house.  May I have your attention?  YOU NEED TO MAKE THIS NOW!  This was incredibly delicious and was a huge hit at the party.  I could see it being on the table at Thanksgiving and Christmas, as well as on a Sunday night with your family.  It does take a little while longer than I expected to get set up, but it was well worth it!

This recipe calls for a number of fresh herbs, including rosemary.  I suggest using as many fresh herbs as you can.  That being said, I cheated and used dried rosemary.

Unfortunately, it really doesn't work to make this too far in advance.  I assembled extra (enough to fill a 9x9 pan) and let it sit overnight to bake the following evening.  The cream separated, and although it still tasted fine, it was not nearly as good as making it immediately before use.  That being said, the site I found this recipe claims you can make it 6 hours in advance.

Ingredients

(makes 9x13 pan)
1 1/2 pounds Yukon Gold potatoes
1 1/2 pounds sweet potatoes (yams)
2 cups heavy whipping cream
1/2 stick butter
2 cloves garlic, minced
1 tablespoon minced fresh parsley
1 tablespoon minced fresh rosemary
1 tablespoon minced fresh sage
1 tablespoon mince fresh thyme
1 1/2 teaspoon fine sea salt
3/4 teaspoon freshly ground black pepper
1 1/4 cups (packed) coarsely grated or finely shredded Gruyere cheese, or a combination of Swiss and Gruyere.

Directions

Preheat the oven to 400 degrees.

Peal all of the potatoes, clean, and cut into 1/8 inch-thick rounds.  I did this using my food processor, which saved some time.  A mandolin would also make a quick job of this.  Place the sliced potatoes in a large bowl of water.

Combine cream, butter, and garlic in a medium saucepan, and bring to a simmer. Chop up all herbs, and mix together in a bowl.  In another small bowl, combine salt and pepper.

Drain the potatoes, and dry well on a kitchen towel.  After dry, transfer half of the mixture to a buttered 9x13 baking dish.  Sprinkle with half of the salt and pepper mixture, followed by half of the herb mixture, and half of the cheese.  Repeat the process again, first adding the remaining potatoes, then salt, then herbs, then cheese.  Pour the cream mixture over the top of everything.  Initially, it won't seem as though there is enough liquid-- do not be alarmed.  Press the potatoes down into the liquid as much as you can.  Cover with foil, and bake for 30 minutes.  Then, uncover, and bake about 25 minutes longer, until most of the liquid is absorbed, and the top of the gratin is golden brown.