Cut the haddock fillet into 1-inch cubes. Barely cover with salted water and cook. Set aside to cool.
While fish is cooling, cut the pork into 1/4 inch cubes and fry until crisp in a large heavy kettle. Drain the cubes on paper towels and pour off all but 4 Tbsp. of the fat. In this fat, cook the chopped onions over low heat until transparent. Add the potatoes and enough of the fish liquor to cover them. Simmer gently until heated thoroughly.
Add the fish to the chowder mixture. Add quart of milk and evaporated milk. Set aside until serving time. It improves the flavor of the chowder greatly to let it stand for several hours before serving. Be sure it is piping hot when bringing it to the table. Biscuits and pickles always go with a good chowder.