How to Make the Ultimate Umami-Bomb Vegetarian Demi-Glace
1 1/2 pounds fingerling potatoes, cut into 1/2-inch rounds
1/4 cup extra-virgin olive oil
10 ounces white mushrooms, thinly sliced
1 onion, thinly sliced
Salt and freshly ground pepper
1 teaspoon minced sage
1/2 teaspoon minced rosemary
1 scallion, thinly sliced
Preheat the oven to 350°. Bring a large saucepan of water to a boil. Add the potatoes and cook until just tender, about 10 minutes. Drain and gently shake out the excess water.
In a large ovenproof skillet, heat the olive oil. Add the mushrooms, onion and potatoes, season with salt and pepper and cook over moderate heat, stirring occasionally, until lightly browned, 10 minutes. Stir in the sage, rosemary and scallion and roast in the oven until browned and sizzling, about 10 minutes longer. Serve right away.