Line 15x10x1-inch pan with foil. Butter foil.
In 2-quart saucepan, mix butter, corn syrup, water and sugar. Cook over medium heat until sugar dissolves and mixture boils, stirring constantly. Cook until candy thermometer reaches soft-crack stage (290°F). Remove saucepan from heat. Quickly stir in almonds. Pour mixture into buttered foil-lined pan. Let stand 2 to 3 minutes to harden.
Sprinkle chips over hot toffee; let stand 1 to 1 1/2 minutes to soften. With knife, swirl softened chips over toffee. Refrigerate about 30 minutes or until chocolate is set. Break toffee into serving-size pieces.