Place the blueberries and raspberries in separate bowls.

In each bowl, add 1 tablespoon lemon juice, 2 tablespoons cornstarch, 1/3 cup sugar and a pinch of salt.

Stir to combine the ingredients in each bowl. Set the bowls aside.

Preheat the oven to 350 degrees Line a baking sheets with parchment paper and set aside.

Roll out the puff pastry into a long rectangle and transfer to the prepared baking sheet.

Brush with the melted butter and sprinkle the breadcrumbs evenly across the pastry sheet.

Place skewers down the middle of one half of the pastry sheet as a guide.

On the left side of the skewer spread out the raspberry mixture. Repeat with the blueberry mixture on the other side.

Fold the plain side of the puff pastry over the side with the berries.

Brush the top with the beaten egg.

Place in the oven and bake for 30 minutes.

Remove from oven and let cool for 15 minutes.

Transfer the strudel to a wire rack and place it over the parchment lined baking sheet.

Let strudel cool completely.

Whisk together the powdered sugar with the milk or cream until it forms a smooth white glaze. The mixture should be thick and pourable. If it is too thin or runny, whisk in more powdered sugar, one tablespoon at a time to thicken the glaze.

Pour the glaze evenly over the top of the cooled strudel. You can cover it completely or make a drizzle pattern.

When the glaze has hardened, transfer to a plate, cut and serve.