1Preheat the oven to 350F.
2Melt the butter in a medium bowl in the microwave. Stir in the brown sugar, egg and vanilla. Add the flour, baking soda and salt and stir until almost combined; add the chocolate chunks and blackberries and gently stir until blended.
3Spread into a greased or parchment-lined 8×8-inch pan and bake for 25 minutes, until golden and the edges are starting to pull away from the pan. Serve as-is or topped with ice cream.