Blend 1 large egg, room temperature*, 1 cup peanut or vegetable oil, 1 Tbsp. fresh lemon juice or distilled white or unfiltered apple cider vinegar, 1½ tsp. agave nectar or mild honey, 1 tsp. Dijon mustard, ¼ tsp. MSG or ½ tsp. Asian mushroom seasoning, pounded to a powder, a pinch of garlic powder or 1 small garlic clove, finely chopped, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a small bowl with an immersion blender until thick and creamy. Blend in a little water if needed; you want mayonnaise to be spreadable. Taste and season with salt and/or add more lemon juice if needed. Cover and let sit 30 minutes before using. (Or, you can use a regular blender. Blend together all ingredients except oil; gradually add oil through a funnel with the motor running.) Do ahead: Mayonnaise can be made 1 week ahead. Keep chilled.
