Old fashioned potato knishes

I invited my friend Paul to come over and make knishes with me, I'd never tried them before. We used the following dough recipe which is from Joe the Pastry Guy

Traditional knish dough

2 cups flour
3/4 teaspoon baking powder
1/2 teaspoon salt
1 beaten egg
1/2 cup vegetable oil
1 teaspoon vinegar
1/2 cup water

Mix dry ingredients in a bowl, put wet ingredients into a well in the middle of the dry ones, stir vigorously until melded, knead in the bowl for a minute, cover with saran wrap and let rest for an hour.

Here is the filling we made:

Filling for potato knishes

1-1/2 pounds of potatoes cut in halves or quarters. We did not peel them.
2 onions chopped up in the food processor (next time I will use three)
A big bunch of parsley chopped up in the food processor
1 tablespoon of oil
2 tablespoon of butter
1/2 teaspoon salt
lots of pepper
an egg (or an egg white, or an egg yolk) for glazing

Put water on to boil as you scrub your potatoes and cut them. Put them in the coldish water, bring to a boil, and cook around 20 minutes. Meanwhile, start frying the onions over low heat in the salt, oil and butter. The longer, the better, we cooked ours almost half an hour, stirring constantly, but they could have cooked longer. Towards the end we added the parsley and pepper.

We each had a rolling pin. I divided the dough into four balls, he rolled out two and I rolled out two, as thin as possible, they came out about 18" long and about 4" wide. Along the long side we put a long log of filling about an inch tall, spread some oil on the still exposed part of the dough, and rolled the dough up so it wrapped around the filling almost twice.

Then you mash down on the filling about every 2-1/2 inches with your hand and where you mashed, pick up the end, twist where you mashed (like a sausage casing) and cut where you twisted. You end up with a little pillow twisted closed at both ends. Squish it around and put it with one of the twisted ends down on the baking sheet, then I pushed into the middle top (at the other twist) to make an indentation in mine but Paul didn't do that, so his are the ones that look sort of open at the top.

Beat the egg and glaze the knishes (we used our fingers). Bake for about 25 minutes at 375 degrees. This made about 25 knishes at the size you see in the picture.