Preheat oven to 350 degrees

Place the 3/4 cup mashed potatoes in a large mixing bowl. Gradually beat 1/4 cup of the water into the potatoes, beating until smooth. Add remaining water, 1 teaspoon vanilla and cake mix. Mix just until blended. Pour mixture into ungreased 9x13x2 cake pan. Bake until deep golden brown, about 30 minutes. Cool completely.

To prepare topping, combine blue mashed potatoes and cream cheese in a medium bowl. Beat until smooth. Add powdered sugar and butter. Beat until well blended. Stir in remaining vanilla and fold in whipped cream. Spread mixture over cooled cake. Chill several hours or overnight. Before serving, top with strawberries.