Arrange the fish on a broiler pan or baking sheet. Spray the fish with olive oil and sprinkle liberally with seafood seasoning. Broil until firm and opaque. Cool the fish and flake with a fork. Dress with the juice of the lime.
In a large mixing bowl, stir to combine the softened cream cheese, sour cream, coriander and cumin. Add the chiles and 1 cup of the Jack cheese, the cilantro or parsley, fresh or dried dill, salt and pepper to taste and the halibut flakes.
Spray a casserole or baking dish with olive oil. Arrange 3 to 4 spoonfuls of the filling on the edge of each tortilla and roll the enchiladas. Set into the casserole seam-side down. Pour the heavy cream over the top of the casserole, just enough to cover, and cover with the remaining Jack cheese and the grated Parm. Chill, covered, for a make-ahead meal. Bring to room temp before baking.
Preheat the oven to 375 degrees F and bake the casserole brown and bubbly, 45 to 50 minutes. Top with avocado, onions and parsley or cilantro.