Kohlrouladen in Saure Sahnesauce

Last night was Rouladen night: Jon and Cati brought over Schweinerouladen and we made these Kohlrouladen, which turned out great:
For the filling:
1 lb ground beef
1 medium onion, finely chopped
4-5 cloves garlic, finely chopped
paprika, thyme, marjoram, black pepper, salt to taste
a splash or two of Riesling
1/4-1/2 cup breadcrumbs

Brown the beef, adding salt, pepper and paprika as it cooks. Remove it from the pan and set aside. Add the onion and garlic to the pan and allow them to cook until they start to brown. Deglaze with a splash of wine.
Add back the beef, along with the herbs and another splash of wine. Adjust seasonings and then add enough bread crumbs to soak up any remaining liquid.
Set the filling aside.

Preparing the rolls:

Start with a head of cabbage; we were unable to find wirsing (curly cabbage?) , but savoy worked out ok. Remove the core and then throw the whole head in a big pot of well salted, boiling water for a couple of minutes. Pull the head out of the water and carefully remove as many of the outer leaves as are soft. This is the part where you burn yourself and curse a lot. Once you've exhausted the soft leaves, throw the head back in the water for a couple more minutes and repeat the process. Burning yourself is optional on this and subsequent steps.
After you've got enough softened leaves, cut away any particularly thick bits of stem from each leaf and then assemble the rolls using 2-4 leaves and a few tablespoons of filling per roll. (Andrea did this, so I don't have much detail to provide). Tie them off with 3 pieces of twine and set aside.
Heat some olive oil in a pan that can be covered and, in batches, brown the assembled rouladen on all sides. Be really careful here to not rip or otherwise mangle them.
Once all the rouladen are browned, deglaze the pan with some Riesling, add the rouladen back to the pan, and add enough chicken stock to come halfway up the rolls.
Toss in some juniper berries, a good grind of black pepper, a bit of thyme and marjoram, and some bay leaves. Bring the liquid to a boil, reduce the heat, cover, and simmer for 45-50 minutes. After about 10 minutes, crush the juniper berries a bit to release their flavor.

Finishing the sauce:
When you're ready to serve, carefully remove the rouladen and add some cornstarch/water to the sauce. Simmer until the sauce thickens, whisk in some sour cream, and adjust seasonings.
Serve the rouladen topped with the sauce.