How to Make the Ultimate Umami-Bomb Vegetarian Demi-Glace
3 tablespoons unsalted butter
2 tablespoons extra-virgin olive oil
2 pounds mixed braising greens, trimmed and coarsely chopped
2 tablespoons water
Kosher salt and freshly ground pepper
In a large heavy saucepan, melt the butter in the olive oil. Add the greens and water and season with salt and pepper. Cover and cook over high heat until wilted and tender, 2 to 3 minutes. Drain the greens and keep warm until serving.