Stir sugars, whipping cream and corn syrup into a large bowl. Microwave on high for 10 1/2 minutes stirring with wooden spoon every 3 - 4 minutes. Remove from microwave. Place bowl in sink of cold water. Put butter and vanilla in and stir for a few seconds. Leave sit for 5 minutes. Stir until gloss disappears and candy thickens. Pour into 8" square buttered pan. Refrigerate for 1 hour. Cut into squares.
Not a NESTLÉ®-tested recipe.