Place all dough ingredients in the bowl of your mixer and knead into a smooth dough. Remove from the mixer bowl and set aside.

In a medium saucepan, sauté leek and onions in oil till golden.

Peel the potatoes while they are still warm. Place warm potatoes, sautéed leek and onions, salt, and pepper in the bowl of your mixer. Mix on high for about two minutes until smooth.

Preheat oven to 375 degrees Fahrenheit (190 degrees Celsius).

Remove an eighth of the dough for a crisscross design and set aside.

Divide remaining dough in half. On a piece of Gefen Parchment Paper, roll one half into a 1/4-inch thick rectangle.

Spread 1/2 of the filling lengthwise on the center of the dough. Fold dough over so that the sides overlap each other. Place seam-side down onto a lined cookie sheet. Repeat with remaining dough, except for the piece you set aside.

Roll out the piece of dough you set aside. Cut into 12 12×1/2-inch strips, six strips for each log. Drape strips over log to form crisscross pattern. Tuck ends under. Brush logs with beaten egg.

Bake uncovered for 45 minutes to an hour, until golden brown.