Wash and slice the mushrooms into slices. Dice the onion and mince the garlic. Combine the stock and the rosemary in the measuring cup, being sure to crush the rosemary finely between your fingers before adding. Give the rosemary a chance to soften while the recipe proceeds.

Dry sautee the mushrooms until dry and squeaky. Add onion and garlic, and cook for an additional 2-3 minutes, stirring occasionally, until the onion is cooked and softened. Sprinkle the mixture with the flour, and stir to combine. Cook for 1 minute. Stir in the stock until combined. Then add in the remaining ingredients, and stir until completely combined.

Bring the sauce to a simmer. Then reduce heat to medium-low and continue simmering until the gravy reaches your desired thickness, about 1-5 minutes (depending on how thin you like your gravy), stirring occasionally. Taste, and season with additional salt, pepper and/or rosemary if needed. Remove from heat and serve. This is awesome over biscuits or with oven-baked vegetables.