Drain the soaked dried chilies and, using a mortar and pestle, pound them with the salt, sliced galangal, and sliced lemongrass until roughly combined and fragrant.
Add the shallots, garlic, kaffir lime zest, coriander root, black peppercorns, and shrimp paste to the mortar and continue pounding until the mixture is smooth and well combined.
Add the roasted peanuts and pound everything into a thick, smooth paste to finish the Panang curry paste.
Set the paste aside in the refrigerator until ready to cook.
Clean and thinly slice the beef brisket or shank and set the slices aside to drain briefly.
Heat a skillet over medium heat and add 1 tablespoon of the prepared Panang curry paste; sauté for 1–2 minutes until fragrant.
Add the beef slices to the pan and stir-fry until just cooked through.
Pour in the coconut milk, stir to combine with the beef and paste, then season with palm sugar and light soy sauce. Simmer briefly to meld the flavors and adjust seasoning to taste.
Turn off the heat, plate the curry, and garnish with shredded kaffir lime leaves and thinly sliced red chili. Serve hot.
