In a pot over medium heat, combine pork face and enough water to cover. Bring to a boil, skimming scum that accumulates on top. Lower heat, cover and simmer for about 45 minutes to 1 hour or until meat is tender but not falling apart. With a slotted spoon, remove meat and drain well.
Add pig brain to pot and cook for about 8 to 10 minutes. With a slotted spoon, remove brain and transfer into a bowl. With a fork, mash until smooth. Set aside.
Over hot coals, grill pork for about 4 to 6 minutes on each side or until crisp and slightly charred. Allow to cool to touch and dice.
In a large bowl, combine pork meat, onions, ginger and chili peppers. Add calamansi juice and toss to combine. Add mashed pig brain and stir until well-distributed. Season with salt and pepper to taste.