Make the scones 

1. Line a baking sheet with parchment paper.
2. Using the large holes of a box grater, grate the butter. Transfer to a bowl and place in the freezer.
3. In a medium bowl, whisk together the heavy cream or sour cream, discard and egg yolk.
4. In a large bowl, add the sugar and lemon zest. Using your fingertips massage the zest into the sugar to release it’s oils. Add the flour, sugar, baking powder and salt and whisk to combine. 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. Add the berries and gently combine.
5. Pour the dough onto a work surface and wait it together to form a 2 inch disc. Cut into 8 wedges. Place on the sheet pan and freeze until firm, about 30 minutes or up to 8 hours. If freezing for longer then 8 hours, wrap the scones in plastic wrap in a freezer safe bag.
6. Preheat the oven to 375. Brush the tops of the scones with cream and sprinkle with sugar. Bake for 22-25 minutes, or until golden and cooked though.
7. Allow to cool before glazing.

To make the glaze

1. Sift the powdered sugar into a bowl.
2. Place the raspberries into a fine mesh strainer set over another bowl. Smash the berries releasing as much juice as possible. Measure out 2 tablespoons of raspberry juice and add the the bowl of powdered sugar along with the cream. Scrape the seeds of half a vanilla bean and whisk until smooth and creamy.