Split vanilla bean lengthwise. Using the tip of a sharp knife, scrape seeds from the center into a small saucepan; add bean. Add remaining ingredients to pan; cook and stir over medium heat until heated through, 5-7 minutes. Remove from heat; let stand, covered, 15 minutes to allow flavors to blend. Discard vanilla bean. Store in an airtight container in the refrigerator up to 4 days. Stir before using.