2 pounds boneless beef chuck, cut into 1-inch pieces 2 tablespoons all-purpose flour 1 teaspoon salt 1/2 teaspoon black pepper 2 tablespoons vegetable oil 1 large onion, coarsely chopped 2 garlic cloves, chopped 3 tablespoons water 1 1/2 tablespoons tomato paste 1 cup beef broth 1 cup Guinness or other Irish stout 1 tablespoon Worcestershire sauce 2 teaspoons drained brined green peppercorns, coarsely chopped 2 fresh thyme sprigs Rough puff pastry dough 1 large egg, lightly