Directions

1. Position an oven rack in the center of the oven and preheat the oven to 325ºF/160ºC/gas 3. Melt the butter. Using 1 tablespoon of the melted butter, generously butter a 9-in/23-cm by 13-in/33-cm baking dish. Set aside.
2. To make the streusel topping, combine the remaining melted butter and vanilla in a small bowl. Set aside. Place the oats and brown sugar in the bowl of your KitchenAid® Stand Mixer fitted with the flat beater. Attach the KitchenAid® Sifter + Scale Attachment to your mixer. Close the ingredient valve. Weigh the flour, spices, and salt in the ingredient hopper, taring the scale between ingredients. Turn the mixer to medium-low speed, open the ingredient valve, and sift the flour mixture into the mixing bowl. While mixing, pour the butter mixture down the side of the bowl and mix just until incorporated, about 1 minute. (Don’t overmix or the streusel topping will turn into one big clump rather than a crumbly mixture.) Turn the mixer off, transfer the streusel topping to a bowl, and set aside. Wipe out the mixing bowl and paddle attachment.
3. To make the fruit filling, in a medium bowl, gently stir together the blackberries, sugar, and salt. Set aside.