Mix the oatmeal, flour, sugar, baking soda and salt in a bowl.
Soda will make crumble even more crumbly and tender, but it is not necessary to use it to prepare a traditional version of crumble.
Add the butter to the dry mixture and rub everything together with your fingers into a crumb. Put the bowl of crumbs in the refrigerator while you prepare the filling.
If you think there are too many crumbs, you can put the excess in the freezer and use it another time. Frozen crumbs do not need to be defrosted – just sprinkle it on the berries.
Preheat the oven to 200°C.
To prepare the filling, put the berries in a large bowl and gently mix them with sugar, corn starch and vanilla extract.
Put the berry mixture in a baking dish (20 cm in diameter).
Spread the dough crumbs evenly over the filling.
Bake the pie on the middle level of the oven for 35-40 minutes or until the crumb turns golden and its filling begins to bubble.
Remove the finished roll from the oven and cool completely.
If desired, serve it with vanilla sauce or vanilla ice cream.
Enjoy your meal!