Preheat oven to 350 degrees F. Line a baking sheet with parchment paper.
Combine flour, 3/4 cup (75 g) of the parmesan cheese, chives, baking powder, salt, and baking soda in bowl of a stand mixer fitted with paddle attachment. Mix until combined.
Add the butter and beat for about 20-30 seconds until mixture looks like large, loose crumbs.
Whisk creme fraiche, buttermilk and egg together in a medium bowl until combined.
With the mixer running on low, add in the creme fraiche mixture and mix for just another 10-15 seconds, until dough just comes together. It may be wet and sticky.
Remove bowl from mixer and turn the dough over with your hands a couple times to fully mix in any loose bits of flour.
Turn out dough onto prepared sheet and form dough into a roughly 8 inch circle, about 1 inch thick.
Whisk egg yolk and brush over the top of the dough.
Sprinkle remaining parmesan and the black pepper evenly over the top of the dough.
Score the dough into eight equal wedges with a knife.
Bake for 35 to 45 minutes, rotating halfway through, until scones are golden brown on top.
Let cool on wire rack for 30 minutes, then cut into 8 wedges.
Serve immediately, or store in an airtight container for 2 to 3 days.