Step 1: Sift flour and salt into a large mixing bowl.

Step 2: Use a spoon to push the egg yolk through a fine sieve into the flour.

Step 3: Add the raw egg and mix well.

Step 4: Beat in butter 1 tablespoon at a time.

Step 5: Place dough on a floured surface and knead until smooth and elastic, then wrap in waxed paper and refrigerate until firm (at least 30 minutes).

Step 6: In a heavy skillet, melt 2 tablespoons butter over medium heat; saute the onion and rutabaga until the onion is soft and transparent (5 minutes).

Step 7: Put the onions, rutabaga, and beef through a meat grinder twice if you have one, if not just chop them up as fine as possible.

Step 8: Melt the remaining 4 tablespoons butter over medium heat, and add the meat mixture.

Step 9: Cook over low heat, stirring occasionally, until all of the liquid has evaporated and the mixture is thick enough to hold its shape.

Step 10: Remove from heat and let cool, then stir in 1 egg, and season with salt and pepper.

Step 11: Preheat oven to 350°F.

Step 12: On a lightly floured surface, roll the dough out into a 13x8" rectangle (1/8" thick).

Step 13: Spoon the filling down the center of the rectangle lengthwise, leaving about an inch of space on each end.

Step 14: Lightly brush the long sides with cold water, then fold one of the long sides over the filling and the other side over the top of that.

Step 15: Brush the short ends with cold water and fold them over the top, enclosing the filling.

Step 16: Place pastry seam side down on a baking sheet and brush the top evenly with the remaining scrambled egg.

Step 17: Bake in preheated oven until rich golden brown (30 minutes).

Step 18: Slice pastry diagonally into 1.5" long pieces and serve as an appetizer or with soup.