Heat a medium skillet over medium heat. Once hot, add olive oil. Add the onions and mushrooms to the hot oil. Sauté for 6-8 minutes, until the mushrooms release their juices and are tender.
Add the garlic and saute for another minute, until aromatic and browned.
Sprinkle in ¼ cup all-purpose flour. "Cook" until lightly browned, stirring with a whisk as needed. The oil, mushroom juices, and flour will combine into a paste.
Slowly pour in the vegetable broth while whisking consistently. Add the soy sauce, sage and freshly ground black pepper. Reduce heat to a simmer over medium-low. Continue to whisk the gravy occasionally to prevent a film from forming.
Simmer until the gravy coats the back of a metal spoon without falling off, or until desired thickness is reached. Taste for salt and enjoy!
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Notes
Mushrooms: I prefer baby bella mushrooms for their flavor but white or cremini also work.
Storage: Keep refrigerated for 3-4 days. You can freeze the gravy in a closed container for up to 3 months. Let thaw completely in the fridge before reheating on the stove or in the microwave.
Reheating: Reheat on the stove over medium heat. You may need to add a splash of broth since it will thicken as it sits.
To make in advance: Gravy can be made up to 72 hours (3 days) in advance of serving. Keep refrigerated in a closed container. Reheat on the stove over medium heat. Add a splash of vegetable broth, as needed, to thin the gravy.
Gluten-free option: Make this recipe gluten-free by replacing soy sauce with tamari. Use a gluten-free all-purpose flour mix, such as Bob’s Red Mill, in place of standard all-purpose flour.
Gravy texture/consistency: This a chunky mushroom gravy, but it can be pureed if you prefer smooth gravy. To puree, add the gravy to a blender. I recommend removing the center part of the blender lid and covering it with a paper towel while blending to allow steam to vent. Be careful while blending and make sure not to overfill the blender, as the hot gravy will build up pressure. Pulse the gravy until it reaches your desired consistency.