There's a trendy, Cambodian-inspired sandwich shop in Manhattan called Num Pang that makes a pretty mean tofu sandwich. Such was the inspiration behind my very own version. Mine traces its roots back to Indonesian cuisine, though, with a peanut dressing that's common on dishes like Gado Gado.
Also, just as an aside: While writing this recipe I suddenly realized this would have been really good with some cucumbers and cooked bean sprouts instead of lettuce. Just a thought.
*Note: Fermented shrimp paste is sold in Asian grocery stores and can usually be found in the same aisle as the soy sauce. It is sold in two varieties: just the paste and the paste in soybean oil (more common). The latter is perfectly fine; just make sure to get mostly paste and not too much oil when spooning it into the dressing.
**Note: The "dressing" should be thick. I put "dressing" in quotes because it will not resemble a dressing in the sense most cooks are expecting. In all honesty, it will look more like a thick hummus or dip.
Combine the peanuts and sugar in the bowl of a food processor and pulse until combined. With the machine running, gradually add the water until slightly grainy while still runny. It should not turn creamy like peanut butter; there should still be some texture.** Blend in the sambal oelek or Sriracha and fermented shrimp paste, if using.
In a bowl or shallow dish, mix together the first 7 ingredients until the sugar is dissolved. Add the tofu and marinate for at least ½ hour and up to 2 hours to let the tofu absorb the flavors.
Then, preheat a gas grill or cast-iron grill pan over medium heat. When hot, add the tofu and grill until grill marks appear, about 5 minutes on each side.
Slather the baguette halves with peanut dressing and make 2 sandwiches. Slice the tofu again into thinner slices, if desired, and add the tofu to the bottom bread slices. Then add the lettuce, cilantro, and jalapeño, if using, and the top slices. Serve.