Prepare the banana flower: Remove the tough outer petals, take the inner florets, and remove the hard pistil and scale. Thinly slice the florets and soak them in a bowl of water mixed with lime juice or vinegar to prevent browning and reduce bitterness. Let sit for 15–20 minutes, then drain well.
Toast grated coconut (if using): Lightly toast it in a dry pan until golden and fragrant. Set aside.
In a large bowl, combine the drained banana flower slices, shallots, chilies, lemongrass, and herbs.
Add toasted coconut and belacan (if using).
Drizzle in lime juice, a little coconut milk if using, and season with salt and sugar to balance the tang.
Toss everything gently but thoroughly.
Let it sit for 10–15 minutes so the flavors mingle beautifully.