Preheat oven to 375°F.

Peel and core the apples. In a large bowl grate the apples. Add the cinnamon and sugar, if using. Set aside for 30 minutes.

Line a medium bowl with a clean, dry kitchen towel. Place the grated apples in the towel and wring out as much moisture as possible, transferring to a second towel if necessary. In another bowl, add the grated apples.

Dampen a dish towel and spread over a smooth work surface. Remove the wrapping from the phyllo dough and spread one layer over the dampened towel. Brush with melted butter. Add a second, third and fourth layer on top, brushing each layer with the melted butter.

Scatter ground walnuts on the top layer, leaving a 1/2 inch border on both ends. Spread the grated apples on the walnuts. Fold the borders in and roll up the pastry lightly with the help of the kitchen towel. Place the strudel, seam side down, on a baking sheet lined with parchment paper. Brush the top with melted butter. Bake until golden brown, 30-45 minutes. Cool on a wire rack, sprinkle with confectioners sugar. Cut into slices, serve warm with whipped cream.