Warm the oil in a saucepan over medium heat. After 90 seconds when the oil is hot, add thinly sliced bird's eye chilies, minced garlic, makrut lime leaves, and Indonesian bay leaves. Sauté until fragrant, about 2-3 minutes.
Mix in lime juice (or calamansi juice), tamarind concentrate, tamari (or soy sauce), kecap manis, sugar (palm sugar, coconut sugar, or brown sugar), and corn starch dissolved in water. Stir continuously until the sauce thickens to a glossy consistency. This should take about 2-3 minutes. Set aside.
Cut 14 oz. (396 g.) firm tofu into 8 equal squares.
Coat tofu cubes with tapioca starch (or cornstarch) until evenly covered.
Place a pan over medium-high heat and add neutral-tasting frying oil. Heat the oil for about 2 minutes until it shimmers slightly, indicating it's hot enough for frying. Carefully add the coated tofu cubes to the hot oil. Fry them until they turn golden brown and crispy, around 3-4 minutes on each side. Use tongs or a slotted spoon to turn the tofu cubes for even frying. Remove the tofu from the oil and let it drain on a wire rack.
If using fresh shallots, you can fry them in the same oil you used to fry the tofu until they're crispy. If using prefried shallots, skip this step.
Place sauce down on a plate under the tofu, and garnish the tofu with fried shallots, crushed peanuts, sesame seeds, minced chives, cilantro, and optionally some additional sliced bird’s eye chilies and additional kecap manis.