Place 3 cups (690 G) Thai sticky rice in a medium bowl and cover with cold water by at least 1 inch (2 ½ cm). Cover with plastic wrap and soak overnight at room temperature. After the rice has soaked, drain and set aside.
Fill the large pot with 3 inches (7 cm) of water and bring to a steady simmer over medium-high heat.
Cut out a circle of parchment paper large enough to line the steamer insert and come 2 inches (5 cm) up the sides.
Place the parchment in the insert, add the rice, and spread in an even layer. Place the insert in the pot, cover with the lid, and steam until the rice is translucent and tender, 20-30 minutes. Turn off the heat, but keep the rice covered so it stays warm while you prepare the larb.
Toast the remaining ⅓ cup (75 G) rice in a small pan over medium-high heat, stirring constantly, until light golden brown, about 5 minutes. Immediately pour the rice into a small bowl and let cool completely.
Grind the toasted rice in a spice grinder or mortar and pestle until finely ground. Set aside.
Heat the chicken stock in a wok or large pan over medium heat. Once the stock is steaming, add the pork. Break up the meat with a wooden spoon and cook gently, stirring occasionally, until just cooked through and no longer pink, 8-10 minutes. Turn off the heat and stir in the garlic, shallots, lemongrass, and galangal.
Add the fish sauce, lime juice, chiles, scallions, mint, cilantro, and toasted rice to the pork mixture and stir to combine. Season with more fish sauce, if desired.
Serve the larb with the sticky rice, cabbage leaves, cucumbers, bean sprouts, and lime wedges.