In the bowl of a stand mixer, using the paddle attachment, combine 1 ½ cups flour, whole wheat pastry flour, powdered sugar, yeast, and salt.

In a saucepan or microwave safe dish, heat milk and butter until warm (120°–130°F). Add to flour mixture. Blend at low speed until moistened. Mix in egg yolks. Beat 2 minutes at medium speed. Switch to the dough hook, on low speed gradually add the remaining flour (add more or less as necessary) until dough clings to the hook and cleans the sides, but not the bottom. Knead 8 minutes, until smooth but still slightly sticky. Shape into a ball. Place in greased bowl, turn. Cover, let rise until double about 60 minutes.

Prepare quark filling: Mix together quark, egg yolk and powdered sugar. If necessary, thin plum jam.

Prepare streusel topping: In a medium bowl, mix together flour, sugar, and cinnamon. Mix in melted butter with a fork until crumbs form. Set aside.

Preheat oven to 350°.

When the dough is risen, divide the dough into 12 equal pieces. Shape each piece in to a ball. Roll each ball into a circle. Fill each circle with quark filling. Wrap it into a “purse” shape.

Line a baking sheet with parchment paper. Put each kolach onto a prepared baking sheet with seam down. Press each kolach in the middle. Brush it with egg wash and fill holes with plum filling. Sprinkle it with streusel topping. Bake for about 20 minutes until golden brown.