Sift the flour into a large bowl (my grandma would always use this white, metal, enameled bowl). Make a well, crumble the yeast in it, add about 100 ml lukewarm milk and a tablespoon of sugar. Let the yeast grow for about 15 minutes. Make sure the milk is neither cold nor hot. Cold milk prevents the yeast from growing and hot milk kills the yeast. Alternatively, you can make the starter in a separate bowl by mixing the milk, yeast, sugar and a bit of flour and add it to the flour later with the rest of the ingredients. I like to make it all in one bowl.
Once the yeast is bubbly, add the rest of the milk mixed with the yolks, melted butter, oil, rum, and salt. Mix with a wooden spoon into smooth dough. Leave the spoon in the bowl, sprinkle dough with a little flour, cover with a clean kitchen towel and let rise for 30 minutes in a warm place.
Prepare your fillings according to the instructions bellow.
Knead the dough a few times to get some air in. Let it rise for another 30 minutes. It should double in size and become soft. When you touch it, it should spring back.
You can use two different techniques to shape your kolache. Shape little balls from the dough and place them on a greased cookie sheet. Then make a hole in each ball with a glass covered with a kitchen towel and dipped in flour. I prefer using a rolling pin. Flour the surface and the rolling pin. Roll the dough into a 1-inch thick sheet. With a glass or cookie cutter, cut out rounds and place them on a greased cookie sheet.
Fill each kolach with different fillings. You can even layer two fillings, or put a dollop of each filling in every kolach.
I decorate them by putting a sliced almond on the poppy filling, a raisin on the cheese filling and a crumble topping on the plum filling.
Preheat the oven to 400°F (200°Celsius). The kolache will be raising some more while the oven is heating up. Right before putting them in, brush them with the egg wash from leftover egg whites. Put them in the oven and make sure you lower the oven temperature to 350°F (180°C) after the first 5 minutes of baking to ensure even baking.
Bake for about 15-25 minutes until golden brown on the edges. Let them cool on a wire rack.
Sweet cheese filling:
Soak the raisins in rum. Mix all the other ingredients together. If you’re using cottage cheese, you might want to puree it in a food processor to get the smooth consistency. Add the raisins with rum.
Poppyseed filling: Mix the poppyseeds with the milk in a small pot and cook while stirring constantly until it thickens, about 2 minutes. Add all the other ingredients.
Plum filling: Mix all the ingredients.
Crumb: Mix the flour, sugar and butter with your hands until it becomes a crumb.