Hjónabandssæla

Preheat the oven to 190°C (375°F). Line a baking sheet with parchment paper.

Combine the oatmeal, whole wheat flour, regular flour, brown sugar, and baking soda (if using) in a large mixing bowl.

Cut the semi-soft butter into small pieces and add to the dry ingredients. Use your fingertips to rub the butter into the mixture until it resembles coarse breadcrumbs.

Beat the egg in a small bowl, then stir it into the butter-flour mixture until a dough forms.

Divide the dough into 8 equal portions and flatten each into a circle about ½ cm thick on the prepared baking sheet.

Place a small dollop of rhubarb jam or stewed prunes in the center of each dough circle, then fold the edges up and over the filling to create a partially enclosed pastry, leaving some filling visible in the center.

Bake for 20-25 minutes until the pastry is golden brown and the edges are crisp.

Remove from the oven and allow to cool on the baking sheet for 5 minutes before serving warm.