Raspberry Walnut Oat Bars with Yogurt Swirl

Steps

1. Heat the oven to 350°F (175°C) and line an 8-inch square pan with parchment, leaving an overhang.
2. Spread the walnuts on a small tray and toast in the oven for 6 to 8 minutes until fragrant; let cool.
3. In a large bowl, whisk the oats, flour, brown sugar, baking powder, salt and cinnamon, then stir in the toasted walnuts.
4. In a small bowl, whisk the melted butter, egg and half the vanilla, then stir into the oat mixture until evenly moistened.
5. In another small bowl, stir the Greek yogurt, honey, lemon zest and the remaining half of the vanilla until smooth; this is the yogurt swirl.
6. Press about two-thirds of the oat mixture firmly into the pan.
7. Scatter the raspberries over the base, then dollop the yogurt swirl between the berries and drag a knife through it to marble.
8. Crumble the remaining third of the oat mixture over the top in small clumps, pressing lightly.
9. Bake 35 to 40 minutes, until the top is deep golden and the edges are set.
10. Cool in the pan on a rack for 30 minutes, then chill 30 minutes so the bars firm up.
11. Lift out by the parchment and cut into 12 bars. Keep leftovers in the fridge.