How to Make the Ultimate Umami-Bomb Vegetarian Demi-Glace
1/4 cup plus 2 tablespoons extra-virgin olive oil
1 pound mixed mushrooms, such as shiitake and oyster, stemmed and thickly sliced
Salt and freshly ground pepper
2 tablespoons fresh lemon juice
3 cups thinly sliced celery (about 8 ribs)
1 cup Parmigiano-Reggiano shavings (about 3 ounces)
In a large skillet, heat 3 tablespoons of olive oil. Add the mushrooms, season with salt and pepper and cook over high heat, stirring occasionally, until golden, 7 to 8 minutes. Transfer to a plate and let cool slightly.
In a large bowl, whisk the remaining 3 tablespoons of olive oil with the lemon juice and season with salt and pepper. Add the celery, mushrooms and cheese shavings and toss gently. Serve right away.