In a large bowl, heat milk and water until warm - about 30 seconds in the microwave should do. Add the yeast and ½ teaspoon sugar. Whisk together until thoroughly combined and let sit until foamy, about 10 minutes.
Meanwhile, in a small bowl, combine the butter and remaining 1½ teaspoons sugar and stir until smooth. Add the egg yolk and salt and stir to combine.
Add the butter mixture and 1½ cups flour to the milk mixture and stir to combine. Continue adding flour, 1 tablespoon at a time, until dough comes together to form a shaggy ball; it should be tacky but not sticky. Then knead the dough by hand (or with a dough hook attachment) until it’s smooth and elastic - this will take about 5 minutes (or less if using a stand mixer). Shape dough into a ball and place in a lightly oiled bowl, cover and let it rise until doubled in size, about 1 hour. While the dough is rising, prepare the filling and crumb topping.
Make the filling:
In a food processor or blender, purée all the filling ingredients. Refrigerate until ready to use.
Make the crumb topping:
Melt the butter in a small bowl. Add the remaining ingredients and stir until well combined. Transfer to the freezer.
Shape and bake the buns:
Line a baking sheet with parchment paper.
After the dough has risen, punch it down and divide into 6 equal pieces. Gently shape each piece into a ball and arrange 3 inches apart on the prepared baking sheet. Cover buns with a clean kitchen towel and let rise until slightly puffed, about 30 minutes.
Preheat oven to 375 degrees.
Brush tops of buns with melted butter. Using the back of a tablespoon, create an indentation in the center of each bun. Distribute the filling among the indentations.
Sprinkle the chilled crumb topping over the filling.
Bake for 20-25 minutes until golden.
Recipe by Two of a Kind at https://www.twoofakindcooks.com/cottage-cheese-kolaches/