Prepare the Dough: In a stand mixer, combine 3 cups of einkorn flour, 1 cup of spelt flour, and 1 teaspoon of salt. In a bowl, whisk together milk, melted butter, sugar, egg, egg yolk, and sourdough starter. Gradually pour wet mixture into dry ingredients while mixing until a shaggy dough forms.

Knead and Rise: Transfer dough to a floured surface and knead for 8 to 10 minutes. Place in greased bowl, cover, and let rise for 1 hour, then refrigerate overnight.

Make the Filling: Beat together cream cheese, sugar, flour, vanilla extract, and salt until smooth. Chill in the refrigerator until ready.

Prepare Streusel: Combine flour, sugar, and softened butter. Mix until sandy crumbs form, then chill.

Shape the Dough: After refrigerating, punch down dough, cut into 12 pieces, shape into balls, and let rise for 2 to 3 hours.

Fill and Bake: Preheat oven to 350°F. Create indentations in dough balls, fill with cream cheese mixture, sprinkle streusel topping, brush with egg wash, and bake for 20 to 25 minutes.

Cool and Serve: Allow to cool for 10 minutes on baking sheet, then transfer to wire rack to cool for an additional 20 minutes.