Combine crumble mixture, then pour 2/3 of it into a 8×8 inch pan. Bake at 350 for 10 minutes. Place the remaining crumble in the fridge to keep it cold. Add blackberries, raspberries and brown sugar into a glass bowl. Mash with a fork lightly. Add cornstarch, lemon zest and lemon juice then add vanilla and strawberry preserves. Mix. When the crust is done after 10 minutes, pour the filling over the crust. Crumble the remaining crumble from the fridge over the top. Bake at 350 degrees for 30-35 more minutes. Let cool 90 minutes before serving so the bars set up. You can use frozen berries, just let them thaw and remove the juice before you use them.