Make the dough: In a large bowl, whisk together flour, sugar, and salt. Add cold butter cubes and work into flour until mixture resembles coarse crumbs with some pea-sized bits of butter. Slowly drizzle in ice water, stirring gently until dough just comes together. Do not overwork.

Chill the dough: Form dough into a disc, wrap in plastic wrap, and refrigerate for at least 1 hour.

Roll out the dough: Lightly flour work surface and roll chilled dough into a 12×16 inch rectangle about 1/8 inch thick, keeping edges straight.

Cut and fill: Cut dough into 3×4 inch rectangles. Spoon about 1 tablespoon of fruit filling onto half of the rectangles, leaving a border. Moisten edges with water, place plain rectangle on top, and press edges firmly with a fork to seal.

Prepare for baking: Place filled strudels on parchment-lined baking sheet. Optionally brush tops with beaten egg or milk for golden crust.

Bake: Preheat oven to 375°F (190°C). Bake strudels for 20-25 minutes until puffed and golden brown.

Glaze and serve: While strudels cool for 10 minutes, whisk powdered sugar, milk, and vanilla until smooth. Drizzle glaze over warm pastries and let set before serving.