In a mixing bowl, combine the rice vinegar, brown sugar, soy sauce, honey, chili-garlic sauce, toasted sesame oil, and ginger. Whisk well until blended. While whisking continuously, slowly pour in the peanut oil to form an emulsified dressing. Set aside.
Put the spinach in a salad bowl. Drizzle with 3 to 4 tablespoons of the dressing and toss thoroughly.
Equally divide the dressed spinach among 4 serving plates. Distribute the bacon and mushroom slices on top and lightly drizzle them with a little more dressing. Grind black pepper over each salad before serving. (Reserve the remaining dressing for another use in a covered nonreactive container in the refrigerator.)
Most spinach-and-bacon salads include thinly sliced red onion and are served slightly wilted by a warm dressing. Once a year is enough of that sort of spinach salad for my taste. I prefer this version because the room-temperature soy-ginger dressing is so delicious and perfectly complements not only the crisp yet tender spinach leaves but also the accompanying bacon and mushrooms. We serve this salad much more often because, just as we do, our guests always look up and smile after the first bite. To achieve just the right flavor balance, the dressing measurements yield 1½ cups, more than the salad needs; reserve it in the refrigerator for other salads, or try it instead of mayonnaise for your next cole slaw.
⅓ cup rice vinegar
¼ cup dark brown sugar
3½ tablespoons soy sauce
1 tablespoon honey
2 teaspoons store-bought Asian chili-garlic sauce
1 teaspoon Asian-style toasted sesame oil
½ teaspoon grated fresh ginger
½ cup peanut oil or vegetable oil
4 cups baby spinach leaves
8 slices bacon, cooked crisp and cut into ¾-inch pieces
½ cup cleans, stemmed, and sliced button mushrooms
Freshly ground black pepper