Seed tomato and chop fine. In a bowl stir together tomato, olive paste, and basil. Cut mozzarella into thin slices. Coarsely chop arugula and in a bowl toss with oil, salt, and pepper, to taste.
Halve focaccia horizontally and spread bottom half with olive mixture. Top olive mixture with mozzarella, prosciutto, arugula, and remaining focaccia half. Press focaccia gently and cut lengthwise in half and crosswise into thirds to make 6 sandwiches. Cut sandwiches diagonally in half and wrap tightly in plastic wrap. Chill sandwiches at least 1 hour and up to 1 day.
Recipe courtesy of Gourmet Magazine