Fry the potatoes: Peel 2 medium potatoes, peeled and cut into thick fries or rounds and cut into thick fries or rounds. Fry in hot 400 milliliters neutral frying oil (sunflower) until golden and crispy. Drain on paper towels and season lightly with salt. These form the base of the sandwich and absorb all the juices.

Hard-boil the eggs: Place 2 eggs in a saucepan of cold water. Bring to a boil and cook for 10 minutes

Transfer to cold water, peel, and slice into rounds.

Prepare the baguettes: Slice each of the 2 fresh baguettes lengthways without cutting all the way through. Hollow out some of the crumb with your hands to make room for the filling. Spread 2 tablespoons harissa (generous amount) generously over both inner faces — this is what gives the casse-croûte its distinctly Tunisian character.

Layer the filling (order matters): Start with a base layer of the fried 2 medium potatoes, peeled and cut into thick fries or rounds — they absorb the juices and hold everything in place. Then add 240 grams canned tuna in olive oil (e.g. El Manar), drained and flaked, the sliced egg rounds from 2 eggs, 60 grams pitted black olives, 1 tablespoons capers, and 1 tablespoons fresh flat-leaf parsley, chopped.

Season and close: Drizzle generously with 3 tablespoons extra-virgin olive oil and a squeeze of 1 tablespoons fresh lemon juice. Add 0.3 teaspoons black pepper to taste. Press the baguette closed firmly to bind all the layers together. Serve immediately.