1Cut tofu lengthwise into 4 rectangular planks. Carefully place on clean kitchen towel or paper towel; cover with another kitchen towel or paper towel. Gently press to absorb some of moisture. Sprinkle both sides of each slice of tofu with salt and pepper.
2Heat 12-inch skillet over medium heat; spray skillet with cooking spray. Gently place tofu planks in skillet; cook 2 to 3 minutes on each side or until golden brown.
3Meanwhile, in small bowl, stir together mayonnaise, lime juice, 1 teaspoon of the Sriracha sauce and dash salt. Taste; adjust for desired level of spiciness. For a spicier mayonnaise mixture, add remaining teaspoon Sriracha sauce.
4To assemble sandwiches, spread mayonnaise mixture onto each slice of bread. Place handful of arugula on 4 of the slices; top with 1 tofu plank, a few mango slices and more arugula. Cover each with second slice of bread; cut sandwiches in half.