Elegant Springtime Gefilte Fish

Name: Elegant Springtime Gefilte Fish
Ingredients: * 12 ounces skinless cod fillets, cut into 1/2-inch cubes; * 2 1/2 tablespoons olive oil, divided; * 1 small onion, finely chopped; * 1 yellow or orange carrot, finely diced; * 2 ribs of celery, finely diced; * 1 tablespoon finely chopped fresh Italian parsley; * 2 tablespoons finely chopped fresh dill; * 1 1/2 teaspoons finely grated lemon peel; * 1 1/2 teaspoons prepared white horseradish plus additional for serving, (See Caveat 5. above); * 5 1/2 teaspoons coarse kosher salt, divided; * 1/2 teaspoon freshly ground black pepper; * 2 large eggs, beaten to blend; * 4 1/2 tablespoons unsalted matzo meal