To prepare dough: In a mixer fitted with the dough hook, mix dough ingredients until well combined. From into a ball and wrap with plastic wrap. Refrigerate overnight (don’t skip this step, or the dough won't roll out nicely).
Divide the dough into 3 parts. Roll out one part of the dough as thin as possible, using flour to prevent sticking (don't add too much flour or the dough will become too hard). Using the rim of a glass or round cookie cutter, cut 2 ½ inch circles from the dough.
Prepare the filling: Combine all ingredients. You may have some leftover filling.
To assemble: Stretch out each circle slightly and place a teaspoon of filling in the center. Fold dough over to form a half circle. If necessary, wet fingertips and pinch edges together very well.
Fill an 8 quart pot ¾ full with water (about 6 quarts) and a drop of oil. Bring water to a boil. Add up to 20 kreplach into the hot water. Stir and swirl kreplach around with a spoon. When the water boils again, lower the heat. Cover and cook for 20 minutes. Remove the kreplach and place in a bowl with cold water. Let them chill. Drain. Toss drained kreplach in a drop of oil to prevent sticking.
At this point you can freeze them layered with paper between layers.
Before serving: Dip defrosted kreplach into a shallow bowl of breadcrumbs. Some like to add a little sugar to the breadcrumbs (about ¼ cup sugar to 2 cups bread crumbs) while others prefer to dust it with confectioners sugar when serving. Fry in butter or oil. Butter will burn fast, so you can do a mix of butter and oil, or just oil.