For the crumble cake, first prepare the dough.
For the dough, mix flour and baking powder and mix with the remaining ingredients with a dough hook to form a dough.
Shape into a ball on a floured work surface and wrap with plastic wrap. Let rest in the refrigerator for 30 minutes.
Preheat oven to 180 degrees hot air.
For the filling, cut the strawberries into small pieces. Roll in sugar and let stand for a short time.
Line the bottom of a 26 cm diameter greased baking pan with two thirds of the dough and bake in oven at 12 minutes.
Put the strawberries in a saucepan and bring to the boil. Strain and collect the juice.
Mix a few tablespoons of the juice well with the cornstarch so that no lumps form later.
Bring the juice to a boil in the pot and stir in the cornstarch mixture. Now add the strawberries and simmer again briefly.
Remove the base from the oven and let it cool down a bit.
For the crumbles, mix all ingredients and work with your hands until coarse crumbs have formed.
Form an approx. 2 cm wide rim from the remaining dough and press it into the baking pan.
Pour the filling into the hollow thus formed and cover everything well with the crumbles.
Bake the crumble cake in the preheated oven at 180 degrees hot air for 40 minutes until golden brown.