These buttery bars are topped with sweet and tangy blackberries, coconut flakes, and toasted hazelnuts.
Preheat the oven to 400°F.
To make the filling: In a medium bowl, toss the berries with the coconut, brown sugar, orange zest, and salt. Pour the mixture into a 9" square pan or shallow dish and roast for 40 minutes. The berries should be floating in a pool of shallow juice, but not drowning in it. If the berries are drowning, simply pour off some juice. Set aside to cool.
To make the topping: Using an electric mixer, combine the flour, oats, sugar, and salt. With the mixer on low speed, add the melted butter. Keep the mixer running to allow the crumbly mixture to come together in big clumps. Add the vanilla and mix until everything holds together when squeezed.
To make the bars: Lower the oven's temperature to 350°F. Line a 9" x 13" pan with parchment, and clip the parchment to the sides of the pan.
Measure out 7 cups of the topping: 4 cups for the base and 3 cups for the top.
Put 4 cups of the mixture into the prepared pan, pressing down firmly to form a solid base. Bake this layer for 15 to 20 minutes, until golden and firm to the touch. Remove it from the oven and cool for 10 minutes.
While the base is baking, combine the hazelnuts with the remaining topping mixture.
Spoon the roasted fruit over the base. Squeeze the 3 cups of topping into larger clumps, and place them gently on the fruit to form a layer that covers the fruit without any large gaps peeking through.
Return the pan to the oven and bake for 35 to 40 minutes, or until the top is golden brown and crisp.
Remove the bars from the oven and let cool. Remove them from the pan by lifting them out with the parchment paper and setting them on a cutting board. Cut into 24 squares.
