
Do NOT mix. Cover the bowl and set aside for a half hour in a warm place.

Discard the pit. Turn the plum 180 degrees, then score in the opposite direction, only halfway down this time.
Repeat until all the plums have even scored.
Warm the milk slightly, taking care not to boil it. Add the milk and margarine or vegetable shortening to the flour mixture. Knead the mixture thoroughly.
Cover the bowl. Set aside in a warm place for 20 minutes or until the dough doubles in size.
Grease and flour a 10-inch tart pan. Preheat oven to 400 Degrees F.
Roll the dough out into a circle and transfer it to the pan. Crimp the edges to fit the pan.
Puncture the bottom of the tart dough several times with a fork.

Sprinkle one heaping tablespoon of breadcrumbs evenly over the bottom of the crust. This helps absorb the juice from the plums to prevent a soggy crust.
Starting from the outer edges, lay the plums on top of the crust. The cut tips should point up.

Let the tart stand in a warm place for 15 minutes. Bake for 20 minutes.
After removing the tart from the oven, immediately sprinkle with a tablespoon of sugar over the top.
Whip the cream until stiff peaks form. Then beat in the powdered sugar. Tranfer to a bowl.
Remove the tart from the pan and transfer to a serving plate. Serve with the whipped cream on the side.