3. As the parsnips are cooking, preheat the oven to 200 degrees. Rinse the fish in cold water, dry thoroughly, and salt and pepper the fish inside and out. If you have a saute pan large enough to contain all four, great; if not, divide between two pans. Melt the remaining 1⁄4 cup butter over medium-high heat (for two pans, use 2 Tbsp. butter in each pan) and, when bubbly, lay the fish in the pan(s). Cook for 3 to 5 minutes, or until the skin is beginning to brown. Carefully flip the fish with a spatula, and continue cooking on the other side. Test for doneness by inserting a sharp paring knife in the thick flesh just behind the head; if the knife slips right in, it's done. Transfer onto a sheet pan to keep warm in the oven.