Cook the whole cod fish with the bones, parsley stems and bay leaf in the milk over low heat until flaky, about 10 minutes.
Once cooked, remove the cod fish from the milk. Set the milk aside and let it cool for about 10 minutes. Pull the cod fish from the bones and shred into small flakes.
Pour the flour into a mixing bowl. Add the slightly cooled milk, parsley, egg, onion, cod fish, nutmeg, lemon juice, salt, pepper and stir until combined.
Heat about a half inch of vegetable oil in a 12-inch cast iron skillet over medium heat until the oil reaches about 350°F/180°C. Once the oil is heated, use a large spoon to spoon out the mixture into the oil and form pancakes that are four to five inches in size. Cook the pancakes about 3 to 4 minutes per side until they're golden brown on both sides.
Move the pancakes to a wire rack or a plate topped with a paper towel. Let them drain for a few minutes.
Garnish with chopped parsley and serve.
Notes
Presoak your salt cod for about 2 days, changing the water 3 to 4 times until the cod is pleasantly salty.
Add more flour if you prefer slightly fluffier pataniscas.
The nutrition is estimated using fresh haddock in place of soaked salt cod.