Preheat the oven to 180°C and line a 20cm square baking tin with baking paper, leaving some overhang for easy removal.
In a large mixing bowl, combine the plain flour, rolled oats, baking powder, brown sugar and salt.
Pour in the melted Nuttelex Buttery Spread and mix until the mixture forms a sandy, slightly clumpy crumble mixture.
Press 2/3 of the crumble mixture firmly into the base of the prepared tin to create an even layer.
Bake for 10 minutes until very lightly golden on the edges then remove from the oven.
In the meantime, prepare the berry filling by adding the frozen berries, orange juice, orange zest, sugar, cinnamon, cloves, cardamom and cornflour into a separate bowl. Toss everything together until the berries are evenly coated.
Spoon the berry mixture over the partially baked base, spreading it out evenly.
Scatter the remaining crumble mixture over the top, letting some larger clumps form for a textured topping.
Bake for 30-35 minutes or until the top is golden and the berry layer is bubbling.
Allow the slice to cool completely before lifting out and cutting into 9 even bars.