Ingredients

Pierogi wrappers:

1 large egg yolk

1 c. whole milk

1 tbsp. vegetable oil

½ c. water

3¼ c. all-purpose flour

Topping and filling:

4 tbsp. unsalted butter

5 c. finely chopped onion

4 c. leftover mashed potatoes

4 oz. farmer’s cheese

2 tsp. salt

1 tsp. black pepper

Assembly:

2 large egg whites

2 tbsp. water

All-purpose flour as needed

Sour cream or applesauce, for serving

Preparation

  1. To make wrappers, combine egg yolk, milk, oil, and water in a small bowl. Place flour in a large bowl, pour in wet ingredients, and fold together to form dough.

  2. Transfer dough to a lightly floured board and knead for 3 minutes. If too sticky, add small amounts of flour. When dough is smooth, form into a ball, transfer to a small bowl, cover with plastic wrap, and refrigerate for 20 minutes.

  3. To make filling, melt butter in a large pan, add onions, and saute over medium heat, stirring occasionally, until browned, about 10 minutes.

  4. In a large bowl, combine ¾ cup of cooked onions, potatoes, cheese, salt, and pepper. Set aside at room temperature. Reserve remaining onions for topping.

  5. In a small bowl, combine egg whites and water. Set aside for assembly.

  6. Remove dough from refrigerator and divide into three sections. Place one section on a well-floured work surface and roll out until very thin (about 1/16 inch). Cut circles of dough using a round cookie cutter (or a jar lid or juice glass).

  7. Place a heaping spoonful of the filling in the center of each circle, leaving a border. Brush some egg white mixture on half the outer border and fold dough over into a half-moon shape. Crimp edges with a fork.

  8. Transfer pierogi to a floured board or platter. Do not stack. Repeat with remaining dough and filling.

  9. Cook pierogi in batches for 4 minutes in a large stockpot of salted boiling water. Drain and transfer to a serving platter. Repeat with remaining pierogi, allowing water to return to a full boil each time.

  10. Serve with the reserved sauteed onion and oodles of sour cream or applesauce.

Try them fried: Cook in boiling water as above for 2 minutes rather than 4, then saute in butter until golden brown.