Classic old fashioneds are made with angostura bitters, but we liked the way orange bitters accented the almond-floral flavors of the orgeat. We liked Woodford Reserve Orange Bitters best, but the more common Fee Brothers West Indian Orange Bitters also were good. The intensity of the orgeat flavor varies by brand. Taste yours; if it's particularly strong, reduce it to ¼ ounce and add ¼ ounce simple syrup. Mid-range bourbons, such as Bulleit or Jefferson's Very Small Batch, work best for an old fashioned. Save top shelf bottles for enjoying neat.