1. To make sauce, whisk together the peanut butter, lime juice, soy sauce, brown sugar, chili paste, and sesame oil in a medium bowl until smooth.
2. To make the filling, combine the tofu, bell peppers, radishes, cilantro and mint in a large bowl, gently toss.
3. Divide the filling evenly among the lettuce leaves, top each with 1 tbs of sauce. Roll up and serve at once.