Preheat the oven to 180ºC/350F and line a bar tin with greaseproof paper.
Place the flour, corn starch and confectioner’s sugar in a bowl and stir to combine.
Make a well in the center and add the brown butter.
Combine with a pastry cutter or knife until the mixture resembles course breadcrumbs.
Pour two thirds of the crumb mixture into the base of a slice tin and flatten down tightly.
Bake for approximately 10 minutes or until lightly golden on top. Remove and set aside.
For the blueberries, place the fruit, sugar and corn starch into a bowl and stir together. Set aside.
Spoon the blueberries evenly over the base.
Top with clumps of the crumble mixture.
Bake for 50 minutes until golden on top and lightly bubbling.
Remove and allow to cool fully or even cool and refrigerate for 1 hour to set fully.
Slice into even bars and serve.