Ingredients

6 tbsp unsalted butter
1/2 cup minced onion
8 oz minced cremini mushrooms, chopped
2 sprigs fresh thyme, leaves removed and stems discarded (optional) or 1 tsp dried thyme
1 clove of garlic, finely minced
1/3 cup unbleached all-purpose flour
1 cup vegetable broth
1 cup whole milk, cream, or half-and-half
1/4 tsp kosher salt (added to the mushrooms while cooking)
1/2 tsp freshly ground black pepper
2 tbsp cornstarch
6 tbsp water

Instructions

In a 10-inch skillet, heat to medium and melt 3 tablespoons of butter.
Once melted add in the minced onion, stir and sauté until just soft, about 3-5 minutes.
Add in the mushrooms, salt, garlic, and thyme (if using).
Stir and cook until the liquid from the mushrooms is boiled off.
Sprinkle with the 1/3 cup flour, stir and let the flour cook for a minute or two.
Reduce the heat to medium-low and whisk in the whole milk and vegetable broth until smooth.
Cook until it has thickened, about 4 to 6 minutes
To thicken, mix 2 tbsp cornstarch and 6 tbsp water until smooth, add slowly until thickened to the desired consistency

Notes

*go easy so you don't over salt when adding to the recipe you're planning to make. Storing: Store this in an air-tight container for 3-4 days in the fridge or freeze and simply defrost (slowly) when needed.

Cream of Celery Version

Sauté 4 tablespoons shallot, 2 short stalk of celery (depending on size) that has been minced, 2 cloves of garlic with a large pinch of kosher salt and 6 tablespoons unsalted butter until just about soft.

Sprinkle with 1/3 cup all-purpose flour, stir and let the flour cook for a minute or two.

Whisk in a cup of whole milk, cream, or half-and-half plus cup of vegetable broth.

Whisk until smooth and let simmer until thick.