In a saucepan over medium heat, combine fresh blueberries, ¾ cup of sugar, and 1 tablespoon of lemon juice. Bring the mix to a boil, then reduce heat to a simmer. Let it cook for 15 minutes, stirring occasionally until the mixture thickens and resembles a preserve. Remove from heat and refrigerate to cool.

In a mixing bowl, beat together 8 ounces of softened cream cheese and ⅓ cup of sugar until smooth and creamy, about 2-3 minutes. Set aside.

In a large bowl, whisk together 4 cups of all-purpose flour, ¼ cup of sugar, and 1 teaspoon of kosher salt. In a separate bowl, warm 1 cup of milk and sprinkle 2¼ teaspoons of active dry yeast over it. Let it foam for about 5 minutes before combining with 2 eggs, 1 teaspoon of vanilla extract, and the dry ingredients. Mix until a shaggy dough forms.

Gradually add 10 tablespoons of very soft unsalted butter to the dough, mixing until fully integrated and smooth. Knead for about 10 minutes until elastic.

Transfer the kneaded dough into a greased bowl and cover. Let it rise in a warm place for 1 to 1.5 hours until doubled in size.

Once risen, punch down the dough, divide into two halves, roll out each into a rectangle, spread with cream cheese filling, and blueberry preserves. Roll tightly into logs and twist together.

Place twisted babka into greased loaf pans. Cover and let rise for about an hour.

Preheat oven to 350°F. Bake risen babka for approximately 40 minutes, or until golden brown.

Prepare sugar syrup by combining ⅓ cup sugar and ⅓ cup water in a saucepan; heat until sugar dissolves. Brush syrup over cooled babka.