Buttery, crunchy, and perfectly sweet. These berry oat shortbread bars with a crunchy oat crumble topping, berry filling, and shortbread base are the ultimate summer treat.
Preheat the oven to 350°F. Line an 8x10 baking dish with parchment paper.
In a food processor, add all shortbread ingredients. Pulse until combined. You should be able to press mixture together with your hands. Press mixture into the bottom of the prepared baking dish in an even layer. Prick the shortbread a few times with a fork. Bake for 12 minutes.
While shortbread is baking, prepare the jam filling. To a small saucepan over medium heat, stir together berries, lemon zest, maple syrup, and chia seeds. Let jam come to a low simmer then cook for 5 minutes until it has cooked down and berries have burst. In a small bowl, whisk together 1 tbsp corn starch and 1 tbsp water. Whisk corn starch slurry into jam. It will start to thicken immediately, take off heat. Once shortbread is done baking, spread over it in an even layer.
In a food processor, pulse together all crumble ingredients until combined. Sprinkle crumble on top of the jam filling. Bake for 22-25 minutes until top is light golden brown. Allow bars to cool for 10 minutes before slicing.