For dressing, in a screw-top jar combine Blueberry Vinegar, oil, salt, and pepper. Cover; shake well.
In a large bowl combine greens, blueberries, walnut halves, crumbled cheese, and snipped chives. Pour desired amount of dressing over salad. (Cover and refrigerate remaining dressing.) Toss lightly to coat. Divide salad mixture evenly among 4 individual bowls. Garnish with fresh chives and blossoms, if desired. Makes 4 servings.
In a stainless-steel or enamel saucepan combine 1-1/2 cups fresh blueberries with 2 cups rice vinegar. Bring to boiling; reduce heat. Simmer, uncovered, 3 minutes. Stir in 2 tablespoons honey. Remove from heat. Pour mixture through a fine-mesh strainer and let it drain into a bowl. Discard berries. Transfer strained vinegar to clean 1-quart jar or bottle. Add 1-1/2 cups additional blueberries to jar or bottle. Cover tightly with a nonmetalic lid (or cover with plastic wrap and tightly seal with a metal lid). Let stand at least 8 hours before using. (Store vinegar in a cool, dark place for up to 6 months.) Before using vinegar, discard berries. Makes about 3-1/2 cups.