Place the soy curls in a heatproof bowl. Add the boiling water, mushroom powder, Worcestershire sauce, and kecap manis. Stir to coat the soy curls evenly, then set aside for 10 minutes.
Drain the soy curls in a colander and squeeze out some of the excess liquid.
Press the tofu dry and cut it into bite-sized cubes.
Heat the olive oil in a large skillet over medium-high heat. After 90 seconds, when the oil is hot, add the tofu and drained soy curls. Sauté for 7-8 minutes, turning occasionally, until golden on all sides.
Add the onion, scallions, and sliced pepper. Cook for 3 minutes, stirring frequently, until the vegetables become tender and fragrant.
In a small bowl, whisk together the garlic, sugar, vinegar, tamarind, sriracha, and tamari. In a separate bowl, mix together the cornstarch and water until smooth and pour it into the sauce, stirring to combine.
Pour the sauce into the skillet and stir constantly for 2–3 minutes, until the sauce thickens and coats the tofu and soy curls.
Transfer to a serving dish and garnish with sliced bird’s eye chilies, scallions or chives, and minced red onion.