Chili paste is available in most supermarkets in the ethnic section, where you may also find tamarind paste. This tangy, sour-tasting paste is made from the pulp in pods of the tamarind tree, which is native to Asia and northern Africa. Substitute lime juice if you’re unable to find tamarind.
Cut each package of tofu in half lengthwise and again in half widthwise to make 4 blocks. Rub tofu with 2 tablespoons of canola oil and season with salt and pepper.
Dissolve the tamarind paste in 1/3 cup water. Discard any solids. Set aside.
In a medium saucepan, heat 3 tablespoons of canola oil over medium heat. Add the garlic and shallots and cook for 1 minute, or until fragrant. Add chili paste (if using) and peanuts, stirring constantly to prevent burning. Add the peanut butter and tamarind juice, followed by coconut milk. Cover and set aside to keep warm.
Preheat grill to low. Grill tofu blocks for 10 seconds on each of the six sides.
To serve, place 2 blocks of grilled tofu on each plate, pour one-quarter of peanut sauce over it and sprinkle with chopped cilantro.