Lightly oil large baking sheet. Cook sugar and water in heavy medium saucepan over low heat, stirring occasionally until sugar dissolves. Increase heat and boil without stirring until sugar turns caramel color, about 8 minutes. Remove from heat. Stir in cream, then butter (mixture will bubble vigorously). Stir until butter melts. Pour onto prepared sheet. Freeze toffee until firm, about 20 minutes. Break toffee into 2-inch pieces. Coarsely chop toffee in processor using on/off turns. (Toffee can be prepared 1 day ahead. Store in airtight jar in freezer.) Makes about 1 cup candy 09