Prep all ingredients per the instructions above.

Rinse the salt-cured herring filets under cold water to remove excess salt, then pat dry with a paper towel.

Slice the sub rolls lengthwise and lightly toast until just warm and slightly crisp.

In a small bowl, mix the mayonnaise and Dijon mustard. Season with salt and black pepper to taste.

Spread the mayonnaise–mustard mixture evenly inside the toasted rolls.

Layer the onion, sliced pickles, parsley, chives, and herring filets into the rolls.

Add the lemon slices to the sparkling water and gently stir. Add ice cubes as desired.

Serve the broodje haring with potato chips, pickle spears, pear slices, and lemon sparkling water.