Upon seeing eggy's recipe for homemade oyster sauce, I recalled having said I would post a vegetarian version. When I went to my source, Vegetarian Cooking for Everyone, by Deborah Madison, I found that what I had was not a vegetarian oyster sauce at all, but a vegeatrian Nuoc Mam.

So here it is. And perhaps, eggy, you could tell us the difference, because I am clueless here. Thanks.

Vegetarian Nuoc Mam

2 garlic cloves, minced
1 or 2 serrano chiles, minced
2 tablespoons light brown sugar
2 tablespoons fresh lime juice
1/4 cup rice vinegar
1/4 cup mushroom soy sauce

Simply stir everything together in a small bowl.