Tofu with Chili-Pineapple Sauce (Tow Hu Sam Rod)

This sauce is traditionally served with fish (Pla Sam Rod), but we've substituted our old pal tofu here...

1 block of extra firm tofu, diced
1 tsp. finely ground black pepper
4 TB cornstarch
oil for deep frying

2 TB cooking oil
2 red Thai chilis, finely chopped
1 sweet red pepper, chopped
1 medium onion, chopped
1 clove garlic, finely chopped
1 stalk celery, finely chopped
1 cup fresh pineapple, diced into small chunks

Sauce ingredients:

2 TB tamarind water
2 TB water
2 TB palm sugar
2 TB roasted chili paste
1 TB mushroom-flavored soy sauce
1 TB rice vinegar

Combine sauce ingredients. Mix cornstarch and black pepper together. Dredge tofu in cornstarch-pepper mixture, shaking off excess, and deep fry until golden brown. Meanwhile, heat 2 TB oil in pan and lightly stir-fry chilis, garlic, and celery until fragrant. Add onions and red peppers and stir-fry until cooked through. Add tofu and pineapple to pan and stir. Add sauce and stir until well combined. Serve with rice.