Raspberry Dark Chocolate Oat Crumble Bars

Steps

1. Preheat the oven to 350°F (175°C). Line an 8-inch square pan with parchment, leaving overhang on two sides.
2. Make the crumble: in a large bowl, whisk the oats, flour, brown sugar, baking soda, salt and cinnamon.
3. Stir the vanilla into the melted butter, then pour the butter over the oat mixture and stir until evenly moist and clumpy.
4. Measure out about one third of the crumble and set it aside for the topping. Press the remaining two thirds firmly into the pan.
5. Bake the base for 12 minutes, until just set at the edges.
6. While the base bakes, make the filling: in a medium bowl, stir the granulated sugar and cornstarch together, then add the raspberries, lemon juice and lemon zest and toss, mashing about half the berries lightly with a fork.
7. Spread the raspberry filling over the warm base, leaving a narrow border. Scatter the chocolate chips over the filling.
8. Crumble the reserved one third of the crumble evenly over the top, squeezing some into small clusters.
9. Bake 30 to 35 minutes, until the topping is golden and the filling bubbles at the edges.
10. Cool in the pan on a rack for 1 hour, then lift out by the parchment and chill 30 minutes so the filling sets.
11. Cut into 12 bars with a sharp knife, wiping it between cuts.