Fill a large Dutch oven with water to a depth of 1 inch. Bring water to boiling. Place a steamer basket in the Dutch oven. Place peaches in the steamer basket. Cover and steam for 5 minutes or until peaches are tender. Remove peaches from steamer basket and place in a large colander to drain.
Meanwhile, in a small heavy saucepan combine brown sugar and the cornstarch. Stir in water. Stir in half-and-half and corn syrup. Cook and stir until thickened and bubbly (mixture will appear curdled before it thickens). Cook and stir for 2 minutes more. Remove saucepan from heat; stir in butter and vanilla.
Serve peaches drizzled with caramel sauce and, if desired, sprinkled with coarse, raw sugar. If desired top with a scoop of frozen yogurt.