In a bowl, combine flour and sugar; cut in butter until the mixture resembles coarse crumbs. Press into a greased 9x13 pan.

Bake at 350 for 10 minutes.

Meanwhile, for filling, combine sugar and flour in a bowl.

Whisk milk and egg together in a second bowl.

Gradually add sugar and flour mixture to milk and egg mixture, stirring as you go.

Stir in rhubarb. Pour over crust.

Bake at 350 for 40 - 45 minutes or until custard is set.

Cool

For topping, beat cream cheese, sugar and vanilla until smooth.

Fold in cool-whip.

Spread over top of desset and chill.

Store this dessert in the refrigerator.