The custom is to eat Kreplach in the soup on the Eve of Yom Kippur, Hoshana Rabbah, and Purim. This is a traditional food eaten in the chicken soup. The "hidden" meat is an allusion to the Purim miracle which though orchestrated by G‑d's hand, was hidden in seemingly natural events.
(Taken from the Spice anf Spirit cookbook)

 

DOUGH:
1 ¾ cups flour
2 eggs
½ tsp. Salt
3 Tbsp. Oil

FILLING
1 cup ground cooked beef or chicken
1 small onion, grated
1 tsp. salt

DOUGH:
In a large bowl combine dough ingredients together. Knead and roll out thin on floured board. Cut into 3-inch squares or circles.

FILLING:
in a small bowl mix filling ingredients well. See Kreplach illustrated for filling and folding.
Kreplach can now be either boiled and served in soup or sauteed in oil.

SAUTE:
Heat oil over medium flame in 10-inch skillet. Saute boiled kreplach until golden brown on both sides.

Yields: 18 Kreplach
 

Illustrated Guide:

1. SQUARES: On floured board roll dough out as thin as possible without tearing

2. Cut rolled out dough into 3-inch squares. Place a teaspoon of filling carefully in center.

 

3. Bring point 1 up to point 4 and seal edges. Moisten edges with tip of finger dipped in cold water to keep seams closed.

 

 

1. ROUNDS: On floured board roll dough out as thin as possible without tearing

2. Cut 3-inch circles with round cookie cutter. Place a teaspoon of filling carefully in the center.

3. Lift sides 1-2 and 3-4 to meet in center over filling and press edges together.

4. Fold down top of 3-4-2 to middle and pinch edges together forming a triangle. Moisten edges with tip of finger dipped in cold water to keep seams closed.