Mixed Berry Crumble Bars

Make the crumble base and topping:
1 Preheat the oven to 350 Degrees F.
2 Line all sides of an 8x8 inch square baking pan with parchment paper and set aside.
3 In a medium bowl, whisk together the flours, oats, coconut sugar, baking powder, ginger, and salt with a fork.
4 Pour in the melted butter and mix with the fork to combine.  It should look and feel like wet sand.
5 Press about ¾ of the mix into the bottom of the baking pan.
6 Press down to pack the crust with the back of a spatula or your palm.  Place the remaining ¼ of the crumble in the refrigerator and bake the crust for 10-12 minutes until lightly golden.
While the crust bakes, make the filling:
8 In a medium bowl, combine the thawed berries with the coconut sugar. Give the berries a rough mash with a fork to break them up.
9 Mix in the cornstarch, lemon zest, lemon juice, and vanilla.
10 Pour the filling over the prebaked crust and smooth it evenly with the back of a spoon or spatula.
11 Top with the remaining ¼ of crumble and bake for 30-35 minutes until lightly golden and lightly bubbling.
Cool the bars briefly at room temperature then transfer to the fridge until ready to serve.   
15 The colder the bars are, the cleaner they cut so I always refrigerate them for at least an hour or so before lifting out of the pan and slicing up.
14 Then lift out of the pan, slice, and enjoy!  Cut bars should be stored in the fridge for up to 5 days.