The pickled carrots, spicy mayo can be made and the tofu marinated up to a day in advance, making this a great quickie meal or a perfect option when having guests.
Cut tofu lengthwise into 6 equal slices. Arrange the slices on a few layers of paper towels, top with another few layers of paper towels and top with a heavy pan or a book. Let stand for 15 minutes.
Combine lemongrass, 2 Tbsp water, soy sauce and 1 tsp of sesame oil in a dish large enough to accommodate the tofu slices in a single layer or a large plastic zipper bag. Let stand for at least 20 minutes, flipping slices halfway through.
Meanwhile, combine vinegar, 1/4 cup water, sugar, carrots and radish and let stand for at least 30 minutes and up to a day in advance. Add chopped basil.
In a small dish combine mayonnaise, sriracha and remaining tsp of sesame oil. Whisk until smooth.
Heat large nonstick skillet over medium heat. Coat pan with a spray or brush of oil. Remove tofu fro marinate and pat slices dry with paper towels. Cook tofu slices about 3-4 minutes per side until golden brown and crisp.
Spread mayo over both cut sides of baguette and layer tofu, cucumbers and carrot mixture in between.