In a mixing bowl, combine flour and cold butter. Mix until crumbly.

Add sour cream and mix until a dough forms. Wrap in plastic and refrigerate for 30 minutes.

In a small bowl, mix fruit preserves, cornstarch, and vanilla extract until combined.

Preheat the oven to 400°F (200°C). Roll out the dough on a floured surface to 1/8 inch thick.

Cut the dough into rectangles (about 4x6 inches).

Place a tablespoon of filling in the center of each rectangle. Fold over and seal edges with a fork.

Brush the tops with beaten egg.

Place the strudels on a baking sheet lined with parchment paper. Bake for 15 minutes or until golden brown.

In a bowl, whisk together powdered sugar, milk, and vanilla until smooth. Drizzle over cooled strudels.