Traditional kolache filling recipes include canned or dried fruit, butter, sugar, cornstarch, and vanilla or almond extract. Top the filling with a crumble made of flour, sugar and butter.
To make a traditional pineapple filling, drain a 20-ounce can of crushed pineapple, reserving the juice to be used later. Heat pineapple to a boil in a medium-sized saucepan. Remove from heat and mix in 2 tablespoons of melted butter. Let cool to a lukewarm temperature in the saucepan.
Add 2 tablespoons of cornstarch to the pineapple juice reserve. Once the pineapple is lukewarm, add in the juice and cornstarch combination along with 1 cup of sugar. While stirring, cook over medium heat until the mixture turns clear and thick. Finally, remove from the heat and stir in melted butter.
To make a traditional apricot filling, put 12 ounces of dried apricots in a medium bowl and pour boiling water over the apricots. Cover and let sit at least 6 hours to overnight and drain any excess fluid. This process hydrates the apricots.
Once hydrated, warm the apricots in a medium saucepan over low heat, adding in 3 tablespoons unsalted butter, 1/2 teaspoon almond extract and approximately 1/2 cup of sugar to taste. Soften the apricots using a potato masher or create a smoother texture using a food processor. Once soft, remove the filling from the heat to let cool.
For the filling topping, mix 1/3 cup of flour, 1/2 cup sugar and 1/3 cup of butter in a small bowl or food process until mixture crumbles.