Prep. Finely chop enough onion to create 1/2 cup (57.6g). Mince the garlic.
Cook. In a saucepan, whisk together all the ingredients, bring to a boil, reduce the heat, partially cover, and gently simmer until the sauce is thick, chunky, and very aromatic, about 45 minutes.
In most recipes you soak dried mushrooms first, but much of their flavor is lost in the water (notice how it turns brown?). For this recipe, you do not need to soak the mushrooms first. They will soften and give up their flavor in the sauce while it simmers, and nothing will be lost in the soaking liquid.
Pass it through a fine-mesh sieve to remove the solids.
Serve. Chill then serve or refrigerate for up to 2 months.
