Combine the scallions, mayonnaise, mustard, jalapenos and 1/2 tablespoon pickling juice in a bowl. Heat about 2 inches vegetable oil in a large pot over medium heat until a deep-fry thermometer registers 350 degrees. Remove 2 fillets from the milk, shaking off the excess, and dredge in cornmeal to coat. Carefully lower into the oil and fry until golden and just cooked through, 4 to 5 minutes. Transfer to a paper towel-lined plate and season with salt. Repeat with the remaining fillets.