Combine flour and salt in a bowl, add cold butter pieces, and rub with fingertips until the mixture resembles coarse crumbs, about 3–4 minutes.

Gradually pour cold water into the flour mixture, mixing gently until a smooth, elastic dough forms, knead for about 2 minutes and shape into a ball.

Wrap the dough in plastic wrap, then refrigerate for at least 30 minutes to relax the gluten.

Place golden raisins in a small bowl, cover with warm water, and let soak for 10 minutes until plump and tender, then drain well.

In a large bowl, toss sliced Granny Smith apples with cinnamon, sugar, and lemon juice until the fruit is evenly coated.

Stir toasted breadcrumbs into the apple mixture, creating a drier filling.

On a lightly floured surface, roll the chilled dough into a thin rectangle approximately 12x18 inches.

Brush melted butter over the dough surface, leaving a 1-inch border, then spread the apple filling evenly down the center.

Carefully lift the cloth underneath to roll the dough over the filling into a tight log, sealing the edge with melted butter.

Transfer strudel to a parchment-lined baking sheet, brush with egg wash, then bake at 375°F (190°C) for 35–40 minutes.

Let the baked strudel rest for 15 minutes, dust generously with powdered sugar, slice, and serve warm.