On low heat, warm the milk and 4 tablespoons of the butter until the milk is just beginning to steam, but not boiling, and the butter is melted. Remove from the heat.
Pour the milk and butter into a large mixing bowl, then stir in the yeast, sugar, salt, and 1 1/2 cups of flour. Cover the dough and let it rise until it’s bubbling and porous, about 30 minutes.
After the dough has risen, beat together the oil and egg yolks. Pour the eggs into the risen flour mixture and blend. Slowly stir in the remaining flour until the dough comes together and is soft but not sticky. Pour the dough out onto a floured surface and knead for about 5 minutes or until smooth. (Alternatively, you may use the dough hook on a stand mixer and mix until it’s a smooth ball.)
Place the kneaded dough in a lightly oiled bowl and cover. Allow to rise until doubled in size, about 1 hour. (That said, the sugars within the dough become more complex the longer the dough rises. So, if you allow the dough to rise slowly over 4-5 hours, the baked kolaches will be more brown and have a more complex flavor.)
Grease or line a baking sheet with parchment paper. After the dough has risen, punch it down and pull off 8 even-sized pieces. In your hands, roll pieces into balls and then flatten them to about 4-inches round in diameter. Place in the center of each piece of dough a piece of boudin. Fold one side of the dough to the other and seal by pinching on all sides. Cover and allow to rise for 45 more minutes.
After 45 minutes, preheat the oven to 375°F and melt the remaining 4 tablespoons of butter. Brush the tops of the kolaches with half the melted butter, and then bake uncovered for 15-18 minutes or until lightly browned. When you remove the kolaches from the oven, brush the tops with the remaining butter. Serve warm, though they will keep for a couple of days and they also freeze well.
In Texas can find boudin in the packaged sausage section of most grocery stores, as well as specialty meat markets in East and Southeast Texas. If it's not available, it's not difficult to make the filling, and then you can simply place several tablespoons of it in the center of the dough, uncased.
Technically, this dish should be called boudin klobasniky, in keeping with the correct terminology for Tex-Czcech pastries that are rolled around a savory filling, such as sausage, That said, I've never seen this term used at any kolache or doughnut shop.
Boudin kolaches | www.homesicktexan.com