Preheat the oven to 400ºF/205ºC.
Line the pie shell with parchment paper or tinfoil and fill with pie weights or dried beans. Pop it in the oven for 8-10 minutes, until set.
Remove the weights and prick the bottom of the shell with a fork to prevent puffing.
Return the shell to the oven for 2-3 minutes, or until it starts shrinking from the sides.
Once the shell is out of the oven, adjust the oven temperature to 375ºF/190ºC.
While the oven is preheating and the shell is baking, cook the bacon in a medium skillet. When the bacon starts sizzling, add the onions.
Once the onions have softened, add the sauerkraut, white wine and bay leaf, and let it simmer until the liquid is absorbed, giving it the occasional stir.
In a medium bowl, whisk the cream, milk, eggs and nutmeg together.
Removing the bay leaf, slowly stir in the bacon kraut into the egg mixture, then pour it into the crust.
Sprinkle the grated cheese over the quiche and arrange dots of butter around the surface.
Bake for 25-30 minutes, or until set. Cool for 15 minutes before serving.