Place the filets in a bowl and pour on the yellow mustard. Pour the Zatarain's Fish-Fri into a seperate shallow dish, then place the filets in the Fish-Fri until they're coated on all sides.
Grab a large pot, pour in the oil, and heat it up to between 325 and 350 degrees. (Don;t let it get any hotter than 400 degrees.) Carefully place the filets in the oil and cook them for around 7 minutes on each side until they're a deep , golden brown and crispy. Remove each filet and frain it on a row of paper towels.
Place 1-2 felets on the french bread and top with pickles and cole slaw.