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, and cover bowl with plastic wrap. Set bowl aside until the skins loosen and the peppers are cool enough to handle. Using your hands, rub off the charred skin, rinsing your hands frequently under cold running water. Slice peppers in half, and remove the seeds and stems. Cut flesh into 1-inch-wide strips.
2. In a medium bowl, combine the mustard and vinegar. Gradually whisk in the olive oil. Whisk in 2 tablespoons warm water. Whisk in salt and pepper to taste, and set the vinaigrette aside.
3. Slice the loaf of bread lengthwise, and remove crumb; reserve crumb 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 the sandwich tightly with plastic wrap. Set a weight such as a brick or large cast-iron skillet on top for at least 1 hour. When ready to serve, slice sandwich into ten pieces.