Scrape seeds from bean. Combine seeds, bean, and milk in a saucepan. Bring to a boil; remove from heat, and let stand 30 minutes. Discard bean.
Add sugar, gelatin, and salt. Let stand 1 minute. Cook over low heat 5 minutes or until gelatin dissolves, stirring occasionally. Cool completely. Stir in yogurt and corn syrup. Pour into a bowl; cover and chill 8 hours.
Pour into a freezer can of a 1-quart hand-turned or 1/2 gallon electric freezer. Freeze according to manufacturer's instructions. Allow to ripen 1 hour in freezer can. Garnish with mint, if desired.