Whisk eggs, vanilla sugar, and sugar in a mixer (or with an electric whisk) until you reach a fluffy consistency.
Then add the zest and juice of one lemon.
Finally, mix in kefir, buttermilk, and cream.
Briefly whisk everything together until smooth.
Whisk butter, vanilla sugar, and cinnamon in a mixer or with an electric whisk.
Add eggs and cream, then whisk again.
Add baking powder and flour to the mixture.
Stir it together until smooth.
Take a piece of baking paper and place the biscuit mixture on it, shaping it into a long roll.
Wrap the baking paper around the dough to form a long roll.
Chill it until firm enough to slice (approximately 30 minutes).
Preheat the oven to 180 degrees Celsius (356 degrees Fahrenheit), and bake for 15-17 minutes, or until golden brown.
