Put all the ingredients for the dough or base in a bowl and mix with a hand mixer. Note: The dough seems very crumbly at first, so it is best to knead it well again with your hands. This will allow it to form well into a firm dough.
Now grease a small springform pan (diameter approx. 8" (20 cm)) with a little margarine and pour the dough into the pan. Work the dough into the form with your hands.
Then wash, core and quarter the plums. Then spread them on the dough.
For the crumble: mix all ingredients in a bowl and crumble over the plums. Again, the dough is a bit crumbly!
Bake in the oven for about 30 minutes. Then let cool and enjoy!