Preheat oven to 375°F (190°C).

Combine flour and salt in a large mixing bowl. Cut in the cold butter until coarse crumbs form.

Beat the egg with chilled water in a small bowl, add to the flour mixture to form a ball, then refrigerate for a while.

Sauté onions in a skillet over medium heat until translucent; add shredded cabbage and cook until wilted, about 5-7 minutes.

Stir in sharp cheddar, sour cream, salt, and pepper into the cabbage mixture until well combined.

Roll out dough on a floured surface to about 1/8 inch thick and place it into your pie dish, leaving some overhang.

Pour the cabbage mixture into the crust and sprinkle additional cheese on top if desired.

Bake for 40-45 minutes, or until the top is golden brown.