Step 1

Place 1/2 cup of the all-purpose flour, 3 tablespoons of the granulated sugar, and 1 (1/4-ounce) packet dry active yeast in the bowl of a stand mixer. Whisk to combine. Heat 1/2 cup of the whole or 2% milk in the microwave (about 30 seconds) or on the stovetop until warm to the touch (100°F to 110°F). Pour into the flour mixture and stir to combine. Cover and let sit in a warm place until doubled in bulk, about 30 minutes.

Step 2

Meanwhile, cut 6 tablespoons unsalted butter into small cubes and place in a small microwave-safe bowl. Microwave in 30-second intervals until the butter is melted, 30 to 60 seconds total. (Alternatively, melt the butter in a small saucepan over medium heat.) Add 1 teaspoon of the vanilla extract and 3/4 teaspoon kosher salt and whisk to combine. Separate 2 large eggs, placing the yolks in the butter mixture and the whites in a separate small bowl. Whisk the yolks into the butter mixture until combined.

Step 3

When the yeast mixture is ready, add in the egg yolk mixture and remaining 1 3/4 cups all-purpose flour. Knead with the dough hook attachment on medium speed until the dough is soft, smooth, and forms a ball, 2 to 4 minutes. Cover the bowl with plastic wrap; let rise in a warm place until doubled in bulk, 40 to 60 minutes.

Step 4

Coat a 9-inch pie plate with butter, then line with parchment paper with enough overhang to clear the edge of the plate by 1/2 inch. Divide the dough into 12 pieces (about 1 1/2 ounces each), then roll each one into a smooth ball. Place in the pie plate, spacing them evenly apart. Use your finger to press a dimple into the center of each dough ball.

Step 5

Cover and let rise in a warm place until doubled in size, 40 to 60 minutes. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 375°F. Juice 1 medium lemon into a small bowl until you have 1 tablespoon. Add 3 tablespoons apricot, strawberry, peach, or blueberry jam, and stir to combine. (Alternatively, divide the lemon juice evenly between several bowls and add a different jam flavor to each.)

Step 6

Place 4 ounces cream cheese in a medium microwave-safe bowl and microwave until very soft, 15 to 30 seconds. Add 1/4 cup sour cream, 1 tablespoon of the granulated sugar, remaining 1 teaspoon vanilla extract, and 1 pinch kosher salt; stir until combined. Transfer to a resealable plastic bag.

Step 7

When the dough is ready, use your fingers to make a 1x1-inch well in the center of each proofed dough ball. Snip a 1/2-inch triangle from one bottom corner of the bag with kitchen shears. Pipe each well with the cream cheese mixture, stopping when you reach the top of the well (about 1 tablespoon each). Top each well with 1 teaspoon of the jam filling (alternate flavors if using multiple). If any filling spills over, gently widen the dough well with the back of a spoon so it fits.

Step 8

Add the remaining 1 tablespoon milk and 1/2 teaspoon granulated sugar to the reserved egg whites and whisk to combine. Brush onto the exposed dough and sprinkle the brushed dough with poppy seeds.

Step 9

Bake until the kolaches are golden-brown and an instant-read thermometer inserted into the thickest part not touching the filling registers at least 195°F, 20 to 30 minutes. Check after 15 minutes and tent loosely with aluminum foil if the kolaches are browning too quickly. Let cool in the pan for at least 10 minutes before serving.