1Dissolve cornstarch in water in heavy saucepan, stir in sweetened condensed milk and egg yolks. Cook and stir until thickened and bubbly. Remove form heat; add butter and vanilla. Cool slightly. Fold in coconut.
Slice bananas; dip in lemon juice and drain. Arrange them on bottom of pie crust. Pour filling over bananas; cover with wax paper. Chill 4 hours or until set. Top with whipped topping.. Garnish with toasted coconut and sliced bananas, if desired.
Note: to toast coconut: Place coconut in dry nonstick skillet; cook over medium heat, shaking pan or stirring until coconut is lightly browned.