In a stand mixer, combine 3 cups of all-purpose flour and 1 teaspoon of salt. In a separate bowl, whisk together 1 cup of milk, 1/4 cup of melted butter, 1/4 cup of sugar, 1 large egg, and 1 cup of sourdough starter until smooth. Gradually pour this mixture into the flour and mix until a shaggy dough forms.

Knead the dough on medium-low speed for 8-10 minutes until smooth and elastic. If the dough is too sticky, gradually add more flour until it pulls away from the sides of the bowl.

Transfer the dough to a lightly greased bowl, cover it, and let it rise at room temperature for 1 hour. After the initial rise, punch down the dough, cover again, and refrigerate overnight.

Prepare the cream cheese filling by beating together 8 oz of cream cheese, 1/4 cup of sugar, 2 tablespoons of flour, 1 teaspoon of vanilla extract, and a pinch of salt until smooth. Adjust the lemon juice to taste and refrigerate.

For the streusel topping, mix 1/2 cup of flour and 1/4 cup of sugar. Cut in 1/4 cup of cold butter until you achieve coarse crumbs and refrigerate.

After refrigerating the dough, punch it down, shape into a log, and cut into 9 equal pieces. Roll each into a ball and place on a lined baking sheet, covering lightly. Allow to rise for 2-3 hours.

Preheat your oven to 350°F (175°C). Grease a measuring cup to create indentations in the dough.

Gently indent each risen ball and spoon in the cream cheese filling. Brush with a beaten egg wash and sprinkle streusel topping.

Bake for 20-25 minutes until golden brown, rotating halfway through for even browning.

Allow to cool on a wire rack for about 20 minutes before serving.