In a medium bowl, combine the warm milk, active dry yeast, and sugar. Let the mixture sit for 5 minutes until it begins to foam.
In a large bowl, cream together the butter, salt, and eggs until light and fluffy. Add the yeast mixture to the creamed mixture and mix until combined.
Gradually add in 7-8 cups of all-purpose flour, 1 cup at a time, until a soft dough is formed. Turn the dough onto a lightly floured surface and knead for 8-10 minutes, or until the dough is smooth and elastic.
Place the dough in a greased bowl and cover with a damp cloth. Let the dough rise in a warm place for 1 hour, or until doubled in size.
Punch down the dough and turn it out onto a lightly floured surface. Roll out the dough to 1/4 inch thickness. Cut out circles of dough with a biscuit cutter and place on a greased baking sheet. Fill each circle of dough with 1 teaspoon of prune filling.
Brush the kolaches with melted butter and let them rise in a warm place for 30 minutes.
Preheat the oven to 375°F. Bake the kolaches for 15-20 minutes, or until golden brown.
Remove the kolaches from the oven and let cool before serving.
Interesting Facts
Kolaches are traditional Czech pastries that are usually filled with fruit or cheese.
The dough for kolaches is made with yeast, which gives the pastries a light and fluffy texture.
Kolaches can be served as a breakfast, snack, or dessert.