This dish was my mother's favorite part of Grandma's Christmas Eve dinner. I use Spanish mackerel, but Boston (Atlantic) will work fine; add a few minutes to the baking time for the thicker filets.
1-1/2 pounds mackerel filets, pin bones removed
2 cloves garlic, minced to a paste or put through a press
Kosher or sea salt and freshly ground black pepper, to taste
1/3 cup dry bread crumbs
1/4 cup grated Pecorino cheese
1/4 cup (packed) minced parsley
2 tablespoons olive oil
1 tablespoon red wine vinegar
Heat oven to 450°. Place fish in a single layer in an oiled casserole dish. Rub garlic into fish and season with salt and pepper.
In a bowl, combine bread crumbs, cheese, and parsley; sprinkle over fish. In a small bowl, whisk together oil and vinegar; spoon over fish.
Bake 15 minutes; some of the crumbs will be browned and the pan will be crackling. Remove pan from oven and let rest 10 minutes before serving.