Combine brown sugar, 3 tablespoons bourbon, and butter in a small saucepan over medium-high heat; bring to a boil. Simmer 2 minutes or until sugar dissolves, stirring frequently. Stir in 5 tablespoons half-and-half; simmer 10 minutes or until reduced to about 1 cup. Remove pan from heat. Stir in remaining 1 tablespoon half-and-half, 1 teaspoon vanilla, and 1/8 teaspoon salt. Keep warm.