Sausage and Cheddar Stuffed Onions

6 medium yellow onions, trimmed, peeled, and halved pole to pole

3 tablespoons olive oil, divided

¾ teaspoon kosher salt, divided

¼ teaspoon freshly ground black pepper

12 ounces frozen sweet Italian sausage (about 3 links), defrosted, casings removed

½ cup chopped parsley leaves, plus more for serving

1 cup Panko, divided

4 ounces grated white Cheddar (about 1 cup), divided

 

Preheat oven to 425°F. Arrange onions, cut sides up, in a 9-by-13-inch baking dish. Drizzle with 2 tablespoons oil and season with ½ teaspoon salt and the pepper. Add ½ cup water to dish, cover tightly with foil, and roast until onions are tender when pierced with a knife, 45 to 50 minutes. Uncover and let cool slightly.  Meanwhile, combine sausage, parsley, ½ cup Panko, and half the cheese in a medium bowl, breaking up sausage as you mix.