- 1/2 cup extra-virgin olive oil
- 1/2 small onion, finely chopped (1/2 cup)
- 4 ounces baby portobello mushrooms, finely chopped (1 cup)
- 1/2 cup all-purpose flour
- 4 to 5 cups vegetable stock, preferably homemade, as needed
- 1 teaspoon soy sauce, more to taste
- 1/2 teaspoon kosher salt
- 1/4 teaspoon black pepper
- In a large skillet, heat oil over medium-high heat. Add onion and mushrooms; cook, stirring, until well browned, 8 to 10 minutes.
- Sprinkle in flour and cook, stirring, until golden brown, 3 to 5 minutes. Slowly whisk in vegetable stock, a little at a time, until a smooth sauce forms. Simmer 2 to 3 minutes until thickened. Season with soy sauce, salt and pepper. Serve as is, or pass it through a fine mesh strainer.