1. Heat a grill or grill pan to hot; alternatively, heat the broiler. Cook peppers until completely charred, turning frequently so all sides cook evenly, 8 to 10 minutes. Remove from heat. Place peppers in a deep bowl; cover with plastic wrap. Set bowl aside until skins loosen and peppers are cool enough to handle. Using your hands, rub off charred skin, rinsing hands frequently under cold running water. Slice peppers in half, and remove seeds and stems. Cut flesh into 1-inch-wide strips.

2. In a medium bowl, combine mustard and vinegar. Gradually whisk in olive oil. Whisk in 2 tablespoons warm water. Whisk in salt and pepper to taste; set vinaigrette aside.

3. Slice the loaf of bread lengthwise, and remove crumbs; reserve crumbs for another use. Spread the olive paste on the bottom crust, and add the pepper strips. Crumble the goat cheese on top of peppers. Arrange artichokes over goat cheese. Drizzle half of the reserved vinaigrette on top. Arrange prosciutto and salami over artichokes. Drizzle with the remaining vinaigrette. Scatter herbs over meats. Place the top crust on sandwich.

4. Wrap in parchment paper; secure to a wooden cutting board using twine. Rest a brick or cast-iron skillet on top; refrigerate at least 1 hour and up to 4. Just before serving, slice sandwich into 10 pieces.