In a heavy saucepan combine the corn syrup, water, sugar, and vanilla bean. Bring to boiling. Reduce heat. Simmer, covered, about 20 minutes. Remove saucepan from heat. Cool mixture, uncovered, for 30 minutes. Stir in the vodka and the chocolate extract.
Transfer to a jar with a tight-fitting lid. Let the mixture stand for 1 week before serving. Makes 3 cups