- 2-3 sprigs fresh thyme
- 1 bay leaf
- 1 tablespoon whole black peppercorns
- 1 coffee filter or cheese cloth
- 3 large turnips, sliced about 1/8-inch thick
- 3 large Yukon Gold potatoes, sliced about 1/8-inch thick
- 1 cup heavy cream
- 1 cup half-and-half
- 4 garlic cloves, smashed and skin removed
- 1 tablespoon kosher salt
- 3 teaspoons jarred horseradish, drained
- 1 cup Pecorino Romano cheese, finely grated
Preheat oven to 400˚F and butter a gratin dish or casserole. Make a bouquet garni by putting the thyme, bay leaf, and peppercorns in a coffee filter. Tie with string or fold up and keep at the top, seem side up.
In a large pot, combine the potatoes, turnips, cream, half-and-half, garlic, salt, and bouquet garni. Bring to a boil, then reduce to a simmer for about 10 minutes or until the potatoes and turnips are tender. Remove from the heat, taking the bouquet garni and garlic cloves out. Add the horseradish. Spread it into the buttered dish, making sure it’s even. The cream should seep up just around the potatoes, but not cover them. If you have extra cream, try to scoop some out, so it’s not too soupy. Cover the entire top with the grated cheese. Bake until it’s golden brown. Make sure it has thickened up, and the potatoes and turnips are tender. Let it sit a few minutes before serving.