Swordfish Club Sandwich With Horseradish Aïoli

Ingredients

3 tablespoons olive oil
Grated zest of 1 lemon
2 shallots, finely chopped
4 4-ounce 1/4-inch-thick skinless swordfish steaks (cut to fit the bread)

Horseradish Aïoli
1 egg yolk
1 teaspoon Dijon mustard
Salt and freshly ground black pepper
1 teaspoon roasted-garlic purée
1/2 cup olive oil
1/2 cup canola oil
2 tablespoons lemon juice
2 tablespoons freshly grated horseradish

Sandwich
8 slices of black-olive bread cut from Pullman, boule, or peasant loaf
1 red tomato, sliced
1 yellow tomato, sliced
4 ounces mesclun greens
8 thin slices of pancetta, fried until crisp
1 ripe avocado

Instructions

Combine the oil, lemon zest, and shallots in a shallow bowl, add the swordfish, and marinate for 5 hours or overnight.

Horseradish Aïoli
Blend together in a bowl the yolk, mustard, 1/2 teaspoon salt, and garlic purée. Slowly drizzle in the oils, whisking constantly until the aïoli is thick. Stir in the lemon juice and horseradish, and season to taste with salt and pepper.

To Assemble Sandwiches
Grill each slice of bread on both sides and spread one side of each with the horseradish aïoli. Lay out four slices, and place one slice each of red and yellow tomato, a quarter of the mesclun, and 2 slices of pancetta on each. Peel the avocado and discard the pit. Slice the avocado thin, and divide evenly among the four sandwiches.

Remove swordfish steaks from the marinade, and season with salt and pepper. Broil or sauté each steak for about 1 minute per side and place one swordfish steak on each sandwich. Top with the remaining 4 slices of grilled olive bread and slice in half on the diagonal.

Note: Cooking the swordfish just before the sandwich is served ensures that fish will be juicy and medium-rare.