Make a large double layer of foil. Wrap the cilantro stems, garlic, shallots, kaffir lime leaves, thai chile, lemongrass, ginger, cardamom seeds and turmeric in the foil and seal the sides. Set the packet seam side up directly on a burner or in a cast-iron skillet. Cook over moderate heat until aromatic and beginning to smoke, about 5 minutes. Using tongs, transfer the packet to a rack; let cool slightly. The cilantro stems should be tender and the ingredients on the bottom should be lightly charred.

Spoon the coconut milk into a large saucepan. Bring to a simmer over moderately high heat and whisk in the cilantro paste. Whisk in the coconut milk and chicken stock and bring to a simmer. Stir in the pulled pork and season with salt and pepper. Cook until the sauce has thickened slightly, about 10 minutes. Stir in the chopped herbs and season with salt and pepper. Keep warm.

Spread the mayonnaise on the buns and top with the pulled pork, Cucumber, red onion, cilantro and basil leaves. Serve with lime wedges.