Mix together ripe sourdough starter, all purpose flour, granulated sugar and water. Knead the levain until it forms a cohesive ball. Set in a liquid measuring cup and cover for 10-12 hours until the levain has doubled in size and the top is rounded.

Warm the milk in the microwave (about 1 1/2 minutes full power) or on the stove. It should be around 90-100ºF, no warmer. To the bowl of a stand mixer with a dough hook, add the ripe levain, warmed milk, granulated sugar, melted butter, egg yolks, salt and bread flour.

Turn on the dough hook and knead for 10-15 minutes. The dough will be sticky but smooth and shiny. It should pass the windowpane test.

Bulk Fermentation: Put the dough in a container and cover. Set the dough in a warm, 76-80 degree F place for 4-5 hours. Take the temperature of the dough as needed to maintain temperature right around 78 degrees F. This temperature is optimal for fermentation because it balances the metabolic rate of the yeast with the softening point of the butter. If the temperature drops, the fermentation will stall; if it rises too high, the dough can become over-acidified and lose its ability to hold its shape during the bake. At the end of about 4 hours, the dough should be puffed up and feel very elastic. If it doesn't feel this way, let it bulk ferment for another half hour and check again.

Cold Bulk Fermentation: Place the covered dough in the refrigerator overnight or up to 48 hours. This gives more flavor to the dough and makes the dough easier to handle when shaping.

Shape and Proof: Dump the dough out onto a clean countertop. Cut the dough into 24 equal pieces, about 85 grams each. Take each piece of dough and pull/pinch up the sides until it forms a ball. Roll the ball on the counter using your hand in a cupping shape to seal the balls and create tension for the roll to rise.

Line a large baking sheet with parchment paper and place dough balls on the baking sheet, 12 to a pan. Cover the dough and let the buns rise for 3-4 hours. I like to set my covered dough in my oven with the light turned on. This keeps the buns in a warm (78-80 degree F) environment to rise.

You will know the kolache dough has risen when the dough balls are puffed up and feel light and airy. The dough will not be hard or stiff. When you push in on the dough, it will leave a small indentation while springing back just a little bit. If the dough springs back completely and the dough feels hard or compact, let it rise another half hour and check on it again. You may need to warm up the dough if it doesn't seem to be rising much.

Mix Up Cream Cheese Filling: Using a hand mixer, whip together the cream cheese, powdered sugar, egg yolk, flour and vanilla extract. Whip until completely incorporated and thick and creamy, about 3 minutes. Stick a piping bag into a glass and fold the edges over the glass. Transfer the cream cheese mixture to the piping bag.

Prepare Jam: Prepare your favorite jams for the fillings. Put them in piping bags or spoon them into the center of the dough.

Shape and Fill: Once the dough is puffy, risen and aerated, use the bottom of a 16 oz canning jar or a 1/4 cup measuring cup and press down firmly on top of each ball of risen dough, forming a large circle indentation with higher sides. Using your piping bag, fill each kolache with a ring of cream cheese around the edges. Place a teaspoon or two of jam in the center of the cream cheese mixture. Repeat with all 24 kolache.

Bake: Preheat oven to 375 degrees F. Lightly whisk an egg with a teaspoon of water and brush the egg wash on the sides of each kolache. Bake for about 18 minutes until lightly browned and bubbly. Enjoy warm!