1. In a large saucepan, sauté onion in oil until soft and golden.
2. Add minced garlic and stir, sautéing for several additional minutes, until fragrant.
3. Add sliced mushrooms to the pan and sauté over medium heat for 10 to 15 minutes
or until soft.
4. Add salt, teriyaki sauce, sesame oil, red wine vinegar, and brown sugar. Mix well and bring to a boil. Lower heat and simmer for an additional five to 10 minutes.
5. Remove from heat. Blend sauce with an immersion blender or in a food processor, using the S blade, until smooth.