1. Freeze the butter: Using the large holes of a box grater, grate the butter. Transfer to a bowl and place in the freezer.
2. In a medium bowl, whisk together the heavy cream, discard, vanilla and egg yolk.
3. In a large bowl, combine the flour, oats, sugars, baking powder, cardamom and salt. Using a fork, toss the grated butter to coat. Then stir in the sourdough mixture until just combined. Knead the dough a few times to bring it together.
4. Dump the dough onto a clean work surface and use your hands to press and shape the dough into an 8″disc shape. Cut into 8 wedges. Place on the sheet pan and freeze until firm, about 30 minutes or up to 8 hours. To long-ferment: Store the covered scones in the fridge for up to 24 hours.
5. Preheat the oven to 375. Brush the tops of the scones with cream (if you are not making the glaze sprinkle with a little sugar).  Bake for 22-25 minutes, or until golden and cooked though. Let cool a few minutes before glazing.

For the glaze

1. Sift the powdered sugar into a bowl.
2. Place the lingonberries into a fine mesh strainer set over another bowl. Smash the berries releasing as much juice as possible. Measure out 2 tablespoons of juice and add the the bowl of powdered sugar along with the cream. Whisk until smooth and creamy.