In a stand mixer bowl, combine all dough ingredients except the butter. Mix with a spatula until a shaggy dough forms.

Using the stand mixer fitted with the dough hook attachment, knead for 8 minutes on low–medium speed until the dough is elastic.

Add softened butter, 2 tablespoons at a time, kneading thoroughly after each addition. Once all the butter is added, knead for 6–8 minutes more, until the dough is very smooth, supple, and pulls away from the sides.

Grease your hands, shape the dough into a rough ball, then transfer it to a medium, lightly greased bowl. Cover and let rise in a warm place (75–80°F) for 1 ½ to 2 hours, or until almost doubled in size.

In a saucepan, combine cherries, sugar, lemon juice, and salt. Cook over medium heat for 10–12 minutes, stirring often, until the cherries release their juices and start to break down.

Whisk together the cornstarch and water, then pour it in while stirring constantly. Simmer for 2–5 more minutes until thickened and jammy. Remove from heat and stir in vanilla extract. Cool completely before using.

Combine berries, sugar, lemon juice, and salt in a saucepan. Cook over medium heat for 6–8 minutes, stirring often, until juices are released. If needed, stir in the cornstarch slurry to thicken. Simmer until thick and jammy. Remove from heat, stir in vanilla, and cool before using.

In a stand mixer fitted with the paddle attachment, beat the softened cream cheese until smooth and creamy. Add sugar, egg yolk, vanilla, lemon zest, and salt. Beat again until glossy and lump-free.

In a small bowl, combine butter, sugar, flour, cinnamon, and salt. Use your fingertips or a fork to pinch the butter into the dry ingredients until the mixture is sandy and clumpy. Chill until ready to use.

Line two sheet pans with parchment paper. Turn out the risen dough onto a lightly floured surface. Divide into 2-ounce portions and smooth into balls, pinching the bottoms to seal.

On a clean, unfloured surface, roll each ball to help shape and seal, then transfer to your prepared sheet pans, spacing them evenly. Cover loosely and let rest for 15–20 minutes.

Lightly grease and flour the bottom of a small glass or measuring cup, and press down on the center of each dough ball to create a deep well. Fill each with about 1 tablespoon of filling, as desired. Cover loosely and let rise again until puffed up, about 1 hour.

Preheat oven to 375°F (190°C). Brush the border of each kolache with egg wash, then top with a generous sprinkle of streusel. Bake kolaches for 15–18 minutes, or until golden brown and the interior reaches 190°F.