Place a damp towel on a work area and cover with wax paper. Remove 4 sheets of filo from package. Keep the remaining sheets covered with wax paper and a damp towel to prevent drying out. Fold the filo leaves in half like a closed book and unfold one page. Brush with clarified butter and sprinkle lightly with breadcrumbs. Continue turning the pages of the filo, brushing with the butter and crumbs until you come to the center. Do not brush the butter in the center yet. Close the second half of the book over the first and work backward; open the last leaf and continue spreading the butter and crumbs until you come back to the center. Now brush the center with the butter and sprinkle with crumbs. Depending on how thick you want the strudel, spread 2-3 cups of the Cabbage Filling lengthwise on the open filo book, 2 inches from the edge closest to you and 2 inches from the sides. Cover the filing with the closest edge and fold the sides over. Brush the sides with butter and continue rolling up the filo, jelly-roll fashion. Cover a baking sheet with foil. Brush the foil with butter. Place the strudel on the foil, seam side down, and brush it with butter. Refrigerate uncovered until the butter hardens, 15-20 minutes. Repeat with remaining filo and filling. The strudel can be frozen at this point. Preheat oven to 350 degrees. Bake the strudel for 45 minutes or until golden brown. Slice immediately and serve hot with the Sour Cream Dill Sauce and garnish with sprigs of dill.
Cabbage Filling: Melt the butter in a large heavy saucepan over medium heat. Add the flour and stir until dissolved. Add the paprika and mix well. Add the onions and continue cooking for 15 minutes, stirring, to avoid sticking. Add the cabbage, brown sugar, and salt and pepper to taste. Simmer, partially covered, for 1 hour, or until golden brown. Stir occasionally. Remove from the heat and cool. This mixture can be made a day ahead and stored, covered, in refrigerator.
Sour Cream & Dill Sauce: In a bowl, combine all ingredients; cover and chill.