Preheat oven to 400 F. On lightly floured surface roll dough to a 14-inch round. Transfer to an 11-inch tart pan with removable bottom. Trim edges; prick bottom with tines of fork.
Line pastry shell with alumnum foil; fill with pastry weights, dried beans, or raw rice. Bake 15 minutes. Remove foil and weights. Bake 5 to 6 minutes longer or just until pastry starts to turn golden.
Brush with egg white; bake 1 minute longer. Cool completely on wire rack. In large skillet, heat oil over medium heat. Add sausage and mash with fork to crumble into small pieces. Add potatoes, onion, salt, and pepper.
Cook until potatoes are fork tender, stirring frequently, about 20 minutes. Cool to room temperature. Reduce oven temperature to 350 F. Stir dill and mayonnaise into potato mixture; spoon into tart shell.
Bake 30 minutes or until heated through. Cool 10 minutes on wire rack before removing outer ring. Sprinkle with parsley. Serve warm.
Makes 8 servings.