Ingredients
1/4 cup (1/2 stick) unsalted butter
3/4 cup extra-virgin olive oil
2 red onions, thinly sliced
Coarse salt
1 pound mixed wild mushrooms, such as chanterelle, morel, and oyster, wiped clean, large mushrooms sliced 1/4 inch thick and small mushrooms left whole
Freshly ground pepper
3 bunches scallions (about 1 pound), trimmed to 6-inch lengths
6 tablespoons champagne vinegar
Preparation
In a skillet large enough to hold the mushroom mixture without crowding, melt butter with 1/4 cup oil over medium-high heat. Add onions, and season with 1 teaspoon salt; toss to combine. Cook, stirring often, until onions are translucent, 3 to 5 minutes. Add mushrooms, and toss to combine. Season with salt and pepper. Cook, stirring often, until mushrooms are almost tender, 3 to 4 minutes.
Add scallions. Cover; cook, stirring occasionally, until mushrooms and scallions are tender, 7 to 8 minutes.
Stir in vinegar and remaining 1/2 cup oil. Season with salt and pepper.
