01 -
Preheat oven to 175°C. Line a 20×20 cm baking dish with parchment paper, ensuring an overhang for easy removal.
02 -
In a large bowl, blend all-purpose flour, rolled oats, brown sugar, salt, and baking powder until evenly combined.
03 -
In a separate bowl, whisk melted butter with vanilla extract until homogeneous.
04 -
Add wet ingredients to dry mix, stirring until a crumbly dough forms.
05 -
Firmly press two-thirds of the crumb mixture into prepared baking dish, forming an even layer. Reserve remaining mixture.
06 -
In a clean bowl, gently combine blackberries with granulated sugar and lemon juice until fruit is coated.
07 -
Spread blackberry mixture evenly over pressed crust.
08 -
Distribute reserved crumb mixture over blackberry layer, then sprinkle chopped pistachios on top.
09 -
Bake 30–35 minutes, or until topping is golden and filling is bubbling.
10 -
Allow bars to cool in pan for 1 hour. Lift out using parchment, then slice into 12 squares.
11 -
Dust tops lightly with powdered sugar before serving, if desired.