Mushroom and Leek Gratin
- 4 tablespoons extra-virgin olive oil
- 2 pounds large portobello mushrooms (6 to 8), stemmed and sliced 1/2 inch thick
- 2 leeks (white and light-green parts only), cut into 1/4-inch-thick half-moons and rinsed
- Coarse salt and ground pepper
- 1/4 cup dry white wine, such as Chardonnay
- 3/4 cup heavy cream
- 2 tablespoons fresh lemon juice
- 1 tablespoon fresh thyme leaves
- 1 ounce Parmesan, finely grated (1/4 cup)
Preheat oven to 375 degrees. In a large skillet, heat 2 tablespoons oil over medium-high. Working in batches if necessary, add mushrooms and cook, tossing occasionally, until softened, 10 to 15 minutes. Transfer to a paper-towel-lined plate.
Wipe out skillet, return to heat, and add 2 tablespoons oil. Add leeks and season with salt and pepper. Cook, stirring frequently, until softened, 8 minutes. Add wine, and cook until almost evaporated, 2 to 3 minutes. Stir in cream, lemon juice, and thyme leaves.
Transfer leek mixture to a 2-quart baking dish. Top with mushroom slices, overlapping slightly. Sprinkle with Parmesan and bake until edges are bubbling, 20 to 25 minutes. Serve warm.