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 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 rolls.

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

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

Add the strawberries to a bowl and top with whipped cream.

Serve the broodje haring with potato chips, pickle spears, strawberries and cream, and lemon chia sparkling water.