Preheat oven to 350 degrees.  Place the bowl and beaters that you will use to whip the whipping cream for the topping in the freezer to get them nice and chilled.  Prepare an 8×8 metal pan by greasing with soft butter, or spraying with your favorite non-stick spray.

In a medium bowl, combine the shortbread crust flour and sugar.  Dice the stick of butter by slicing the stick in half lengthwise, and then sliced across the entire length (I try to do 16 slices).  Cut the butter into the mixture (I use a pastry cutter) until it resembles coarse crumbs.  Pat into the bottom of the prepared pan.  Bake for 10 minutes.  Remove from oven and let cool slightly on a cooling rack.  

While the crust is baking make the filling. Combine the sugar and flour in a medium bowl and whisk together. Whisk  in cream and eggs. Add in rhubarb and stir until combined. Pour over slightly cooled crust.  Bake for 50 minutes, or until custard is set and no longer jiggles; a slight jiggle still in the center is expected and it will finish cooking once you remove. Remove from oven and cool for an hour on a wire rack.

For the topping grab that bowl and beaters from the freezer and add the whipping cream. Whip on high speed. I prefer to use my stand mixer for this, but a hand mixer works just as well. Gradually sprinkle the 2 Tblsp granulated sugar over the top to incorporate in.  Whip just until the cream reaches stiff peaks (if you stop and lift the beater out of the mixture the whipped cream peak remains upright).  

In a separate medium bowl beat the softened cream cheese, sugar and vanilla together until smooth (I use my stand mixer for this also). Add in the whipped cream and gently fold in; I end up using my stand mixer and quickly beating them together until smooth.  Spread over top of the completely cooled bars. Cover and chill for at least 2 hours before serving.  

Best served cold.  Can be stored in the refrigerator, covered for a week.  Enjoy!