In a large skillet over medium heat, add the white parts of the scallions and salt. Cook for 3 minutes or until the onion is softened, stirring occasionally.
Add the curry paste and garlic and cook for 1 minute, stirring it often. Stir in the tempeh, soy sauce, fish sauce, and maple syrup. Stir together to coat everything evenly, then spread out into an even layer. Increase the heat to medium-high and cook for 5 minutes, undisturbed (to help it brown/caramelize), stirring halfway through. Remove from heat and stir in the lime juice.
In a medium bowl, mix together the peanut butter, lime juice, water, and soy sauce until smooth. If your peanut butter is thicker/pasty, you may need to add a splash more water to loosen it up. Add the cabbage and carrot and toss to coat.
Warm your tortillas. Add tempeh crumbles and top with plenty of slaw, the green parts of the scallions, peanuts, a squeeze of lime, and sriracha (if using).