To make the sweet buns, warm the milk and butter in a medium saucepan, until the butter has melted. Remove from the heat.

Place the flour, sugar, yeast and salt into a kitchen mixer with the bread hook. Add in the milk and butter mixture and begin to knead. Add in the egg and continue kneading for 8-10 minutes on medium-low speed. If you do not have a kitchen mixer, just blend everything in a large bowl and knead by hand, around 15 minutes. The dough should be soft, smooth and elastic. Cover with a tea towel and let rise in a warm spot for 1½ hours or until doubled in size.

In the meantime, prepare the filling by blending together the brown sugar, cinnamon, salt, and butter.

Preheat the oven to 375°F (190°C). Grease 2 pie dishes or line two baking sheets with parchment paper.

On a well-floured surface, use a rolling pin to roll out the dough into a large rectangle that measures roughly 18 × 22 inches (45 × 56 cm), with the longer side directly in front of you. Spread the cinnamon/butter mixture over the entire surface of the dough, spreading it to the edges. Evenly distribute the frozen lingonberries on top. Gently roll the dough horizontally to form a log. Using a sharp knife, cut the log into 12 pieces. Arrange the buns evenly inside the pie dishes. Let the buns rise for 40 minutes. Place in the center of the oven and bake for 30-35 minutes, or until nicely browned and cooked through. Alternatively, bake the buns spaced apart on the parchment-lined baking sheets, 1 sheet at a time, for 10 to 12 minutes or until nicely browned.

While the buns are cooling, prepare the orange glaze. In a small bowl, combine the powdered sugar with the fresh orange juice and zest with a fork to form a semi-thick glaze (adjust the orange juice as you go to get the desired consistency). Drizzle on top of the buns and serve immediately. The glaze will harden as the buns cool.

Refrigerate the leftovers for up to 2 days, reheating when serving.