In a mixing bowl, combine the flour, sugar, and salt. Add in the cold cubed butter and mix until the mixture resembles coarse crumbs.

Gradually add the cold water, one tablespoon at a time, until the dough comes together. Form the dough into a disc, wrap it in plastic, and refrigerate for at least 15 minutes.

While the dough chills, prepare your fruit filling. Sauté apples slightly with some sugar and cinnamon if using, or chop berries and mix with sugar if desired.

Preheat your oven to 375°F (190°C). On a lightly floured surface, roll out the chilled dough to about a 1/8-inch thickness.

Cut into rectangles that are approximately 4x6 inches, leaving enough space between each piece.

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

Cut a few small slits in the top to allow steam to escape.

Place the strudels on a baking sheet lined with parchment paper. Bake for 15-20 minutes or until golden brown.

In a small bowl, combine the powdered sugar, milk, and vanilla extract until smooth. Drizzle over the warm strudels before serving.