1. Warm the milk in the microwave or on the stovetop until it reaches a temperature between 120°F and 130°F. Transfer the milk to a large mixing bowl, whisk in the sugar, and then sprinkle the yeast on top, lightly mixing it with the milk. Let the yeast proof for about 5 minutes until it becomes bubbly and foamy.
2. Incorporate the salt, vanilla, eggs, and egg yolks, along with the cooled melted butter. Whisk until the mixture is smooth. Gradually add the flour, whisking thoroughly after each addition. Once the dough begins to come together, switch to a spatula.
3. Dust your work surface with flour, then turn the dough out. Knead the dough while adding the remaining flour. Continue kneading for 12 to 15 minutes until the dough is smooth and elastic; if using a mixer, this may take about 20 minutes.
4. Return the kneaded dough to your mixing bowl for proofing.

First Proofing

1. Take a small pot and fill it halfway with boiling water, ensuring that the bottom of your bowl does not touch the water. Cover the dough with a towel and allow it to proof in a warm area of the kitchen for 1 ½ to 2 hours, or until it has doubled in size. Change the water every 30 minutes to maintain warmth.
2. For optimal warmth, I prefer to place my dough next to the stove, especially when the oven is in use.

Making the Cheese Filling

1. In a large mixing bowl, beat the softened cream cheese for about a minute until smooth. Then, add the egg, vanilla, sugar, and salt. You can adjust the sugar amount between ¼ and ½ cup based on your taste preference. Mix everything together.
2. Incorporate the tvorog or farmer’s cheese and beat again until you achieve a uniform, creamy consistency.
3. If using cottage cheese, line a large strainer with cheesecloth and add approximately 3 cups of small or large curd cottage cheese. Rinse the curds with cold water and allow them to drain. To ensure the curds are thoroughly dry, wring the cheesecloth.

Making the Vatrushka Buns

1. Carefully turn the proofed dough onto a clean work surface. Use a table scraper or sharp knife to divide the dough into 16 equal portions. Shape each piece into a ball gently, avoiding over-kneading.
2. Prepare two large baking sheets by lining them with parchment paper or silicone mats. Space each ball a few inches apart on the sheets.
3. Create hollows for the filling by pressing the bottom of a glass or jar (about 1 ½ to 2 inches in diameter) into the center of each ball, flattening the dough and forming a cavity.
4. Pierce the hollow with a fork, then fill it generously with the cheese mixture. Top each with a teaspoon of preserves.

Second Proofing & Streusel Topping

1. Preheat your oven to 350°F. Place the sheet pans with the buns on the stove top where it is warm. Allow the buns to proof for 30 to 45 minutes until they become fluffy.
2. For the streusel topping, combine the flour, sugar, and cold butter in a food processor. Pulse until fine crumbs form. Alternatively, you can use a pastry blender for this step.
3. Gradually add the cream, a few teaspoons at a time, while the processor is running. Add just enough cream until the flour and butter mixture forms small crumbles.
4. Using a pastry brush, gently apply the beaten egg around the filling on the dough. Sprinkle the prepared streusel topping over both the filling and the tops of the buns.

Baking Instructions

1. Bake the blueberry and cheese vatrushka buns in the preheated oven at 350°F for 30 to 35 minutes, or until they achieve a rich, golden-brown color. If baking two pans simultaneously, ensure to space out the oven racks and stagger the pans to promote even baking.
2. If you lack two oven racks, place the second pan in the refrigerator to prevent the dough from over-proofing.
3. After baking, transfer the buns to a wire rack to cool for at least 20 minutes, as the cheese filling will be very hot initially!

Storing Instructions

1. These delightful cheese buns can be enjoyed warm alongside a cup of coffee or tea. Once cooled, store the buns in a sealed container or bag. They can be kept at room temperature for up to 2 days and in the refrigerator for up to a week.