-
1
Prepare the dough: Combine the eggs, oil, warm water, salt, and baking powder in a bowl, and beat with an electric mixer on medium speed until well combined.
-
2
Reduce the speed to low and add 2 cups of the flour, 1 cup at a time, mixing well and scraping the bowl down after each addition.
-
3
Using your hands, knead in the last cup of flour, a little at a time, until the dough is pliable and smooth.
-
4
Wrap the dough in plastic wrap and refrigerate for at least 15 minutes or up to 8 hours.
-
5
Prepare the filling: Divide the oil between two large skillets and place them over medium-low heat.
-
6
Add the onions to the two skillets and cook, stirring occasionally, until they are very soft and golden brown, 20 to 30 minutes.
-
7
Meanwhile, bring a large pot of water to a boil.
-
8
Add the potatoes and simmer until tender, about 30 minutes.
-
9
(Testing with a skewer, rather than a fork, will prevent them from breaking up.)
-
10
Drain the potatoes, discarding the water, and return them to the pot over medium heat.
-
11
Heat, stirring, for a minute or two to dry them out a bit.
-
12
Then transfer the potatoes to a very large mixing bowl.
-
13
Add the sauteed onions (including the oil), egg whites, instant mashed potatoes, salt, and white pepper to the mixing bowl.
-
14
Using a hand masher, mash the potato-onion mixture thoroughly.
-
15
Set it aside to cool.
-
16
Cut the chilled dough into 6 equal parts.
-
17
Roll out 1 piece of dough on a board to form a rectangle measuring about 8 x 14 inches (if it sticks, lightly flour the board; keep the remaining dough covered.)
-
18
Place one sixth of the filling in a narrow strip along one long edge of the dough, about 1/2 inch in from the edge.
-
19
Fold in 1/2 inch of both short sides, and roll up the log.
-
20
The whole log (about 13 inches long) can then be stretched to the length of the baking pan you are going to use.
-
21
Repeat with the remaining dough and filling.
-
22
Place the logs on a baking sheet, cover with aluminum foil, and freeze (to facilitate cutting) until solid, 2 to 3 hours.
-
23
When they are solidly frozen, wrap each log in plastic wrap and then in foil, and freeze.
-
24
About 2 hours before serving time, grease a baking sheet with shortening or cooking spray.
-
25
Place as many of the frozen logs as you wish to use, seam side down, on the prepared baking sheet.
-
26
(Each log will yield about 15 knishes.)
-
27
Let them thaw until you can just get a knife through them, about 30 minutes.
-
28
Then cut each log, with out cutting through the bottom layer of dough, into 1- to 1 1/2-inch-wide slices, keeping the log together.
-
29
(This will make it easier to cut them into individual knishes later while keeping the log together for baking.)
-
30
Let the logs thaw completely.
-
31
Preheat the oven to 375F.
-
32
Whisk the egg yolks and oil together in a bowl, and brush the tops of the knish logs with this mixture.
-
33
Bake until golden brown, about 45 minutes.
-
34
Cut into individual knishes, following the lines precut in Step Serve hot.
