Prepare the Dough:

Activate the Yeast: In a small bowl, combine the warm milk and yeast. Let sit for 5-10 minutes until foamy.

Mix Dough Ingredients: In a large mixing bowl, whisk together the flour, sugar, and salt. Add the yeast mixture, eggs, and softened butter. Knead by hand or with a dough hook on a stand mixer for 5-7 minutes, until smooth and elastic.

First Rise: Place the dough in a greased bowl, cover with a towel, and let it rise in a warm place for about 1-1.5 hours, or until doubled in size.

Prepare the Fillings:

Blueberry Filling: If using fresh blueberries, cook them with 1/4 cup sugar until thickened, then let cool. If using blueberry jam, simply set it aside. Stir in cinnamon if desired.

Cream Cheese Filling: In a small bowl, beat together the softened cream cheese, powdered sugar, and vanilla extract until smooth.

Assemble the Babka:

Roll Out the Dough: Once the dough has doubled in size, roll it out on a lightly floured surface into a large rectangle (about 12x16 inches).

Spread the Fillings: Spread an even layer of the cream cheese mixture over the dough, then spoon the blueberry filling over the top.

Roll and Cut: Starting from one long side, tightly roll the dough into a log. Slice the log lengthwise down the middle to expose the filling. Twist the two halves together, keeping the cut sides facing up.

Second Rise: Place the twisted dough into a greased 9x5-inch loaf pan. Cover with a towel and let it rise for 30-45 minutes until slightly puffy.

Prepare the Topping:

Make the Streusel: In a small bowl, combine the flour, sugar, and cold butter. Use a fork or your fingers to create a crumbly mixture. Sprinkle this streusel over the risen babka.

Bake the Babka:

Bake: Preheat your oven to 350°F (175°C). Bake the babka for 45-50 minutes, or until golden brown and cooked through. Cover with foil if it starts to brown too quickly.

Cool and Serve: Allow the babka to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely before slicing.