Seared Halibut with Brussels Sprout Hash

Name: Seared Halibut with Brussels Sprout Hash
Ingredients: 1 pound Brussels sprouts, trimmed and quartered; 4 red-skinned potatoes (about 1 pound); 1/4 cup extra-virgin olive oil; Kosher salt and freshly ground pepper; 1 Gala apple, peeled and cut into small pieces; 1 serrano chile pepper, thinly sliced (remove seeds before slicing for less heat); 1 1/2 teaspoons fresh thyme, chopped; 4 6-ounce skinless halibut fillets; 1/2 cup apple cider; 2 1/2 teaspoons white wine vinegar; 1 tablespoon unsalted butter; Chopped fresh parsley, for topping