This dish makes a great side for a tenderloin or other hearty main. If you want to serve it with something lighter, substitute the Gruyere cheese with more parmesan. You can also substitute the thyme with rosemary for a stronger taste.
3 Tbs. extra-virgin olive oil; plus 1/2 tsp. for the pan
1 lb. Yukon Gold potatoes
1 heaping tsp. very lightly chopped fresh thyme
1/2 cup finely grated Parmigiano-Reggiano
1 cup finely grated Gruyère
Combine the shallots and 3 Tbs. of the oil in a small saucepan and bring to a simmer over medium heat. Reduce to a low simmer; cook the shallots until nicely softened (don’t let them brown), about 2 min. Remove from the heat and let cool completely.
Heat the oven to 400°F. Rub the bottom and inside edge of a 7-1/2-inch tart pan with a removable bottom with butter. You can use olive oil or spray if you want, but I like butter. VERY IMPORTANT – Put the tart pan on a rimmed baking sheet lined with foil. Otherwise, the pan will leak, you will have a smoky kitchen, and you will be cleaning you oven.
If you have way too much time on your hands: Slice the potatoes as thinly as possible (about 1/16 inch) with a chef’s knife. Otherwise: use a food processor to slice the potatoes. Put the potato slices in a mixing bowl, add the shallots and olive oil along with the herbs and toss well to thoroughly coat the potatoes.
Cover the bottom of the tart pan with a layer of potato slices, overlapping them slightly. Start along the outside edge of the tart pan and, making slightly overlapping rings, move inward until the bottom is covered with one layer of potatoes. Sprinkle the potatoes with salt (a generous 1/8 tsp.) and then sprinkle about one-quarter of the Parmigiano and about one-quarter of the Gruyère over all. Arrange another layer of potatoes, season with salt, sprinkle with cheese, and repeat two more times, until you have four layers of potatoes. Top the last layer with more salt and any remaining cheese.
Bake the galette until the top is a reddish golden brown and the potatoes are tender in all places (a fork with thin tines should poke easily through all the layers), 45 to 50 min. The bottom will be crisp and the sides brown.
Let the galette cool for 10 or 15 min. in the pan. It will then be cool enough to handle but still plenty hot inside for serving. Have a cutting board nearby. Run a paring knife around the edge of the galette to loosen it and carefully remove the tart ring by gently pressing the tart bottom up. Slide a very thin spatula under and all around the bottom layer to free the galette from the tart bottom. Use the spatula to gently slide the galette onto a cutting board. Cut into four or six wedges, or as many as you like.