1 package (2 1/4 tsp) active dry yeast
1/2 cup warm water
1/4 cup sugar
4 Tbsp (1/2 stick) unsalted butter, at room temperature
1 egg yolk
1/2 tsp coarse salt
3 1/4 cups flour
3/4 cup milk
1/2 cup cottage cheese
1/4 cup cream cheese
3 Tbsp sugar
squeeze of lemon juice
1 egg yolk
1/4 cup sugar
1/4 cup flour
1 Tbsp melted butter
Also: jam of your choice, and 1 Tbsp melted butter
Make the dough: Sprinkle the yeast and 1 tsp of the sugar in a bowl, let sit 5 minutes until the yeast bubbles. While the yeast is proofing, beat the butter and remaining sugar in a bowl until well combined. Add the salt and egg yolk, beat until smooth. Add the yeast/water mixture, and then the flour and milk. Knead until it comes together in a smooth dough (it will be fairly soft and sticky). Give the dough a few turns on a floured countertop, adding additional flour if needed (try to add as little as needed), and form it into a ball. Return the dough to a bowl, cover, and set aside to rise until doubled in volume, about 1 hour.
In the meanwhile, make the filling: Beat the cottage cheese, cream cheese, sugar, lemon and egg yolk until smooth. Set aside.
Make the crumb topping: Mix together the sugar and flour, and drizzle in the melted butter. Rub together with your fingers until well distributed, yielding a sandy topping with occasional clumps.
Assemble the kolaches: Divide the dough into 16 pieces. Shape into slightly flattened balls, and place them 4x4 on a greased baking sheet about 1/2" apart (I had a particularly narrow baking dish, so I made 15 doughballs, and arranged them in rows 3x5). Brush the doughballs with the melted butter, cover tightly with plastic wrap or a plastic bag, and let rise another 30 minutes.
Preheat the oven to 375 degrees.
When the kolache balls have risen 30 minutes, remove the plastic and have your crumb topping and jam and cheese fillings ready. Using your fingers or a spoon, make a deep indentation in the top of each dough ball, enough to accommodate a heaping tablespoon of filling. Place the filling of your choice in each hole, and then sprinkle the crumb topping over everything (don't worry as the sandy crumbs cover your pretty jam -- the heat of the jam will melt the covering crumbs as they bake). Place the kolaches in the oven, and bake until browned and set, about 30-40 minutes.
These are best eaten the day they're made (in case you needed an excuse).