To make the stewed plums add the halved and pitted plums to a pot.
Preheat oven to 200°C and line a square pan (20 x 20 cm) with parchment paper.
Add brandy and sugar.
Cook over medium heat for 15 minutes until the plums have fallen apart.
Transfer to a blender and add dates.
Purée until smooth.
Place in the pan again and bring to a boil.
Mix corn starch with cold water and pour into plum mixture.
Cook for one minute or until thickened slightly.
To make the short crust, combine all ingredients in a bowl and knead dough until smooth.
Press into the prepared pan.
I recommend to also press the dough into a sides a bit, so that the quite liquid plum purée will stay in place.
Pour the plum purée into the pan.
Prepare the crumbs by combining all ingredients except for cocoa powder.
Form into crumbs and sprinkle half over the plums.
Add cocoa powder to remaining crumble dough, knead again and sprinkle over cake once the cocoa is incorporated.
Bake for 30 minutes or until the crumbs are golden brown.
Let cool completely before slicing and removing from the pan.