Melt vegan butter or olive oil in a large saute pan over medium-high heat.
Add diced mushrooms and stir to coat. Saute for 4-5 minutes, stirring occasionally, until cooked and softened.
Add finely chopped shallot and minced garlic. Cook for an additional 2-3 minutes, stirring occasionally, until softened.
Sprinkle the mixture with flour and stir to combine. Cook for 1 minute.
Stir in the vegetable stock until combined. Then add almond milk, rosemary, and salt, stirring until completely combined.
Bring the sauce to a simmer. Reduce heat to medium-low and continue simmering for 1-5 minutes, stirring occasionally, until the gravy reaches your desired thickness.
Taste and season with additional salt, pepper, or rosemary if needed.
Remove from heat and serve the gravy, topped with an additional sprinkle of black pepper if desired.