Cabbage is a staple in the Ukrainian diet and the leaves are often used as a vehicle for tasty stuffing.
Melt butter in a skillet and sauté onion until tender. Set aside to cool. When the onion is cool, mix with the ground pork, bread crumbs, egg, salt, and pepper until completely incorporated.
Core the cabbage and gently remove the leaves. Trim off any thick ribs at the stem. Place the leaves in a large pot and cover with water. Bring to the boil and cook for 2 minutes, or until the leaves become translucent and tender.
Preheat the oven to 325 degrees and grease the bottom of a 9 x 13 baking dish. Lay the cabbage leaves on a large work surface and place a heaping tablespoon of the pork mixture at the base of each leaf. Roll each leaf tightly from the bottom to the top (like a burrito), tucking in the sides as you go. Repeat until all the filling is gone. Place any extra leaves on the bottom of the baking dish and arrange the stuffed leaves on top. Pour the chicken stock so it just covers the rolls. Place any extra leaves on top to assist with steaming. Cover with foil and bake for 1 hour.
Remove the rolls from the dish and drain off the remaining broth into a small saucepan. Whisk together the flour and sour cream and gradually add to the broth. Cook over medium heat for about 5 minutes, stirring frequently, until the sauce becomes thick.
Arrange cabbage rolls on a platter, cover with sauce and sprinkle with fresh dill.
