Pan Bagna

Hard-boil eggs (see Tip). Peel when cool enough to handle. Set aside one of the yolks for the dressing. Coarsely chop the remaining eggs.

Meanwhile, heat 1 teaspoon oil in a large nonstick skillet over medium-low heat. Add onion; season with salt and pepper. Cook, stirring often, until very tender and light golden, 10 to 20 minutes. (Add 1 to 2 tablespoons water if onions are browning too quickly.)

Cut baguette into 4 equal lengths. Split each piece in half horizontally. Pull out the soft bread from the center of each piece, leaving 1/2-inch-thick shells. Place soft bread in a food processor or blender and process to form fine crumbs. Measure out 1/2 cup of crumbs (reserve the rest for another use).

Mash garlic with 1/4 teaspoon salt with the side of a chef's knife. Transfer to a medium bowl. (Alternatively, mash garlic and salt in a mortar with a pestle.) Add reserved egg yolk and mash with a fork. Whisk in mayonnaise, lemon juice, mustard, anchovy paste and remaining 1 teaspoon oil. Fold in parsley, olives, reserved chopped eggs and breadcrumbs. Season with pepper.

To assemble sandwiches, spread the caramelized onions over the bread-shell bottoms. Mound the egg mixture over the onions. Top with mesclun (or lamb's lettuce) and replace bread tops.