01 -
Combine 1/2 cup flour, 3 tablespoons sugar, and yeast in the bowl of a stand mixer. Heat 1/2 cup milk until warm (38–43°C) and add to flour mixture. Stir to incorporate, cover, and allow to rise in a warm place until doubled, approximately 30 minutes.
02 -
Melt 6 tablespoons butter. Stir in 1 teaspoon vanilla extract and 3/4 teaspoon kosher salt. Separate eggs; add yolks to butter mixture and whisk until blended. Reserve whites in a separate bowl.
03 -
Add egg yolk mixture and remaining 1 3/4 cup flour to the sponge. Knead with a dough hook on medium speed until dough is soft and smooth, about 2–4 minutes. Cover and let rise in a warm place until doubled, 40–60 minutes.
04 -
Grease a 23 cm pie plate with butter, line with parchment leaving 1.25 cm overhang. Divide dough into 12 equal portions (about 43 g each) and roll each into a smooth ball. Arrange evenly in pie plate. Press a dimple into the center of each ball.
05 -
Cover and let rise in a warm place until doubled, 40–60 minutes. Meanwhile, preheat oven to 190°C (375°F) with a rack in the center.
06 -
Juice lemon to yield 1 tablespoon. Mix lemon juice with 3 tablespoons chosen jam. For multiple flavors, divide lemon juice and blend with different jams.
07 -
Soften cream cheese in the microwave. Combine with sour cream, 1 tablespoon sugar, remaining 1 teaspoon vanilla extract, and a pinch of salt. Stir until smooth. Transfer mixture to a piping bag or resealable plastic bag.
08 -
Press a 2.5 x 2.5 cm well into each proofed dough ball. Pipe in cream cheese filling to fill the well (about 1 tablespoon per kolach). Top each with 1 teaspoon jam filling.
09 -
Whisk reserved egg whites with 1 tablespoon milk and 1/2 teaspoon sugar. Brush exposed dough and sprinkle with poppy seeds.
10 -
Bake for 20–30 minutes until golden and the internal temperature in the thickest part (not touching filling) reaches at least 90°C. If browning too rapidly, tent with foil after 15 minutes. Cool in pan for at least 10 minutes before serving.