1. Place the potatoes in a bowl of water along with the salt. Chop the drained anchovy fillets coarsely and set aside. Melt 2 tablespoons of the butter and saute the onion slices for a few minutes.
2. Melt 1 tablespoon of the remaining butter in an 8 by 8-inch glassbaking dish; grease the bottom and sides. I melt the butter in the baking dish in the microwave.
3. Drain the julienned potatoes very well.
4. Place one third of the drained potatoes in the bottom of the buttered baking dish. Top with half of the sauteed onion, half of the chopped anchovies, and black pepper to taste. Top with another third of the potatoes, the remaining onion, anchovies, and more black pepper.
5. Add the remaining potatoes. Pour the cream and reserved anchovy juice over all, and add more black pepper. Melt the remaining 2 tablespoons of butter and drizzle on. Bake in a preheated 375°F oven for 1 hour.
