1) Pastry:
Combine sugar and flour and cut in the margarine.
Knead lightly.
Form into a ball, wrap in plastic. Chill 1 hour.
Preheat the oven to 210 C (425F).
2) Cream Puffs:
Bring water and margarine to a boil.
Add the flour and stir until mixture forms a balls.
Remove from the heat.
Cool slightly, then beat in the eggs, one at a time. The mixture should thick enough to just keep its shape. Make 12-14 balls with a spoon and place far apart on a greased baking sheet.
3) Roll out the pastry. Cut out round cookies with a 6-7 cm (2 1/2") cutter.
Drape them over the balls and press carefully against the baking sheet. Bake until golden, 25-30 minutes.
4) Whisk together eggs, sugar, cornstarch and milk in a saucepan. Heat to boiling stirring constantly. Do not allow to boil. Cool, stirring occasionally. Stir in rum. Whip the cream and fold into the rum cream.
5) Puncture the balls. Fill a pastry tube with rum cream and pipe the mixture into the balls. Top each with a cherry.
