Spil the vanilla pod in half and scrape the seeds onto a pinch of sugar.
Using your knife, massage the seeds into the sugar until it separates.
Zest and juice an entire lemon.
Make kammerjunkere
Heat your oven to 190°C/370°F.
Mix all-purpose flour, sugar, half of the vanilla sugar, salt, baking powder, and lemon zest in a medium bowl.
Crumble the butter into the flour mixture. Add egg and mix it in, then knead the dough until it's cohestive.
Divide the dough into 6-gram pieces and shape each piece of dough into a ball.
Add the balls to a parchment-lined baking sheet, put them in the oven, and bake for 12 minutes.
Take them out and turn the oven down to 150°C/300°F.
Cut them in half, and put them back on the baking sheet, with the cut-side up.
Bake for 18 minutes more and let them cool on a wire rack. Check for crispness and give them a bit more if needed.
Make koldskål
Whip egg yolks, half of the vanilla sugar, and sugar into a creamy white mixture.
Add buttermilk and yogurt and mix.
Season to taste with lemon juice and lemon zest.
Serve immediately, or put in the fridge until you need it. If all of your ingredients were fresh, it stays good for at least a day refrigerated but probably much longer.