1 large celeriac, peeled and sliced 1/8 inch thin, kept in water
4-5 large Yukon Gold, Yellow Finns, or Russets, sliced 1/8 inch, kept in water
2 large brown onions, peeled and sliced ¼ inch thick
6-8 sprigs fresh thyme, marjoram, savory (or a combination), minced
Salt and pepper to taste
1 clove garlic, peeled
¼ cup white wine
1 cup chicken or vegetable stock (more, if needed) OR cream (see Chef Notes below)
Olive oil as needed
1-2 tablespoons butter, cut into little pea sized bits
1-2 cups grated Gruyère cheese, optional (see Chef Notes below)
Heat the oven to 375°F.
Rub the inside of the gratin dish (13 inch oval or 4 quart Pyrex baking dish) vigorously with the garlic, leaving traces of oil over the surface. Then mince the clove and add to the onions.
Heat a pan large enough to hold the onions over medium-high, then film with oil. When hot, add the onions and sauté until golden. Season with salt and pepper and a teaspoon of the herbs.
While the onions cook, heat the stock to a boil.
Once the onions are cooked, place them into the bottom of the gratin dish and level. Sprinkle with some of the herbs. Drain the celeriac and potatoes and mix together. Lay most of them into the gratin dish and sprinkle with some of the herbs and some salt and pepper. Finish off the top of the gratin by evenly placing a row of celeriac, then a row of potatoes, until done, overlapping the slices.
Pour in the hot stock/wine combo to come halfway up the ingredients. Drizzle with olive oil, or use a spritzer if you have one, to get most of the surface. Scatter some more herbs over the surface and season. Scatter the butter bits over the surface and cover tightly with foil. Place the gratin on a foil lined baking sheet. This will contain spills and keep the floor of the oven from getting spattered.
Place into the center of the oven and bake 30 minutes. After 30 minutes, remove the cover and press down on the gratin with a spatula, basting the top with the liquid in the dish. Return it to the oven and continue baking until the ingredients are tender and cooked through. This should correspond to when the last of the liquid cooks off.
Remove from the heat and allow to cool a little so the gratin “sets” and firms up a little.
Chef’s Notes and Tips:
- For a vegan version, eliminate the butter and use vegetable stock. However, the butter adds a nuttiness and helps with achieving a nice golden color.
- If you wish to make a richer version of this, replace half the stock with cream (or all of it!) and grate 1-2 cups of Gruyère cheese, scattering much of it inside the gratin, and sprinkling some on the top.
YIELD: 4-6 servings