Bar Recipe

Prepare oven and pan

Preheat the oven to 350°F (175°C). Line an 8x8-inch square baking pan with parchment paper, leaving an overhang on two sides for easy removal; lightly grease the exposed edges.

In a medium bowl whisk together 1.5 cups all-purpose flour, 1 cup rolled oats, 0.5 cup packed light brown sugar, 2 tablespoons granulated sugar, 1/4 teaspoon fine sea salt and 1/2 teaspoon baking powder until evenly combined.

Stir in 3/4 cup melted unsalted butter until the mixture is evenly moistened and holds together when pressed. Reserve about 1 cup of this mixture for the topping and press the remaining mixture firmly and evenly into the bottom of the prepared pan to form the crust.

Use the bottom of a measuring cup to press the crust tightly and evenly so it bakes into a compact base.

In a small bowl combine 3/4 cup mixed berry jam, 1/2 cup chopped fresh berries (if using), and 1 teaspoon lemon zest. Stir until smooth. If the jam is very thick, warm it for 10–15 seconds in the microwave to loosen before mixing.

Spread the jam mixture evenly over the pressed crust with an offset spatula or the back of a spoon, leaving a small margin (about 1/8 inch) from the edges to prevent overflow during baking.

In a bowl combine 1/2 cup all-purpose flour, 1/2 cup rolled oats, 1/4 cup packed light brown sugar and 1/4 teaspoon ground cinnamon. Add the 3 tablespoons of cold cubed unsalted butter and use a pastry cutter or your fingertips to cut the butter into the dry ingredients until the mixture resembles coarse crumbs with some pea-sized pieces.

Stir in the reserved 1 cup of crust mixture to incorporate a slightly denser texture and pressibility. Sprinkle the crumble evenly over the jam layer. If desired, sprinkle 1 tablespoon coarse sugar on top for sparkle and crunch.

Place the pan on the middle rack of the preheated oven and bake for 28–32 minutes, or until the top is golden brown and the jam is bubbling gently at the edges.

Once baked, remove the pan from the oven and set on a wire rack. Allow the bars to cool completely in the pan, 1.5–2 hours, so the filling sets and the bars firm up for clean slicing.

When cool, lift the bars from the pan using the parchment overhang and place on a cutting board. Whisk together 1 tablespoon powdered sugar and 1/2 teaspoon vanilla extract (add 1/2 tsp water if needed to reach a drizzleable consistency). Drizzle lightly over the cooled bars, if using.

Cut into 12 bars (3 rows by 4 columns) or 9 larger bars (3x3). Store in an airtight container at room temperature for up to 3 days or refrigerate for up to 7 days. For longer storage, freeze individually wrapped bars for up to 2 months.