While coating the tofu cubes: In a pan over medium-high heat, add cooking oil (about 1 inch deep).
Prepare a bowl with cornstarch and a plate or shallow bowl dusted with cornstarch. Generously coat each tofu cubes with cornstarch and transfer them to a plate or shallow bowl dusted with cornstarch. Then, dust the coated tofu cubes again with cornstarch. The point is, they should be well coated.
When the oil is hot enough, fry the coated tofu cubes until golden brown. Put the fried tofu cubes in a strainer to drain excess oil. Remove the oil from the pan (reserve it to use later if you like).
Turn off the heat and transfer the Crispy Tofu Sisig to a serving plate. Enjoy with rice.