Prep the pan: Heat the oven to 350°F (175°C). Line an 8-inch square baking pan with parchment, leaving some overhang for easy lifting. Lightly grease the parchment.

Make the date-cherry filling: In a small saucepan, combine chopped dates, dried cherries, water (or orange juice), and a pinch of salt. Simmer over medium heat for 5–7 minutes, stirring often, until the mixture softens and thickens into a jammy paste. Stir in vanilla and a squeeze of lemon juice. Set aside to cool slightly.

Mix the oat crumb: In a large bowl, combine oats, flour, brown sugar, granulated sugar, baking soda, salt, and cinnamon. Stir well to break up any clumps of sugar.

Add the butter: Melt the butter and pour it over the dry ingredients. Stir until the mixture looks evenly moistened and crumbly. If using nuts, fold them in now.

Build the base: Press about two-thirds of the oat mixture into the prepared pan to form an even base. Pack it down firmly with the bottom of a measuring cup for clean layers.

Spread the filling: Spoon the warm date-cherry mixture over the base. Use an offset spatula to spread it into an even layer. It should reach the edges.

Finish with crumbs: Sprinkle the remaining oat mixture over the top, leaving small gaps so the filling can bubble through. Add a light pinch of flaky salt if you like.

Bake: Bake for 28–35 minutes, until the top is golden brown and you see some bubbling at the edges.

Cool and slice: Let the pan cool completely on a rack. Use the parchment to lift out the slab. Slice into bars with a sharp knife. For the cleanest edges, chill for 30 minutes before cutting.