Make the knish dough:

Crack the eggs in a large bowl. Add salt, baking powder, and oil. Stir with a fork to blend. Add flour gradually, using only as much as you need to form a soft dough. Roden advises using a fork, then your hand to knead the dough. I prefer dumping it on the counter and kneading. Whichever method you use, you’re looking for a dough that is neither sticky nor dry. Don’t add more flour than necessary. I only needed about 1 1/4 cups flour, I did need to add little more oil to make the dough cohere.

Wrap dough in plastic wrap or cover with a clean bowl in a warm place. Allow to rest for at least an hour. Mine sat for just under two hours.

Make the filling:

Slice onions and cook them in the poultry fat, taking care not to burn the onions. If you are a Jew, try not to cry as the smell fills your kitchen.

For Claudia Roden’s potato filling:

Boil the unpeeled potatoes until soft. Peel when cool enough to handle. Mash. Add onions, all the cooking fat, salt and pepper.

For my potatoes, add a heaping 2 tablespoons sour cream to above and mix in.

Set aside while you roll the dough:

The dough should be rolled as thinly as possible. Work from the center outward. Be patient. I flipped the dough a few times, which helped. I also used my hands to gently stretch and flatten it.

When the dough is to your liking, fill and form the knishes. You can make traditional triangular shapes, or you can make the slightly weird shapes I made.

To cut triangles, according to Mrs. Mildred Bellin’s The Jewish Cook Book, published in 1958:

Roll the dough until it is 1/18th of an inch thick. Then cut it into squares. Fill each square with a scant tablespoon of filling, then fold corner to corner to make a triangle. Press edges together firmly.

Set each knish on lightly oiled baking sheet.

To make dumpling shapes, cut the dough into rounds. Fill the center of each round with a scant tablespoon of the filling. Fold over, pulling up edges gently. Crimp together and pinch closed. This is easier than it sounds.

Place each knish on an oiled baking sheet. Paint each lightly with egg wash.

Bake 20-25 minutes, until golden and aromatic. Try not to eat them all at once. If you manage to have any left over, knishes may be reheated in a toaster or regular oven at low heat. A microwave will give you rubber.

Freeze unbaked knishes by placing them in the freezer on a baking tray for 30 minutes. Then either decant into a freezer bag or other freezer container up to three months. Bake from frozen.

Notes:

For the potato filling: Roden is following Jewish dietary law, so her potato filling is very simple. I found it a bit bland, so added sour cream. Use the recipe filling or your preferred mashed potato recipe, bearing in mind this is acting as a filling, so it cannot be runny. No Joel Robuchon potatoes here.

As my spouse dislikes onions, I used one stalk of new garlic.

I sauteed the garlic in leftover goose far from Christmas. Chicken or duck fat also work. You can use butter or oil, but the knish won’t be as good.

Render your own chicken fat by pulling off skin or clumps of fat from a whole bird, slicing it, and melting it in a frying pan over low heat with a little water. Low heat and time are key here. Cracklings, called gribenes in Yiddish, are reason to live. Eat them all yourself. You can also freeze or refrigerate them and add them to anything. Except dessert.