In medium pan add sugar, butter, and water. Cook on medium to medium high stirring constantly until Carmel or toffee color appears. Remove from burner and add vanilla extract, stir and mix well. Immediately pour into 8 to 9 inch round pan and spread evenly. Place 3 chocolate bars on top and wait to melt. Spread chocolate evenly over toffee. Sprinkle chopped pecans evenly over chocolate. Let set until chocolate dry and candy hard. Remove from pan and break into pieces.