1. Combine rice flour and turmeric in a bowl, then whisk in coconut milk and water. Set aside to rest until needed.
2. Combine ingredients of nuoc cham in a small bowl with little bit of water, whisk to combine and season to taste (it should taste sweet, salty, sour and hot).
3. Heat coconut oil in a wok over high heat, add pork, prawns and garlic and stir-fry until just done (1-2 minutes). Remove from pan and clean the pan for the crepes.
4. Heat more coconut oil in the pan over high heat, add a ladleful of batter, swirl to cover pan thinly and cook until golden (3-4 minutes).
5. Scatter pork, prawns, spring onions and bean sprouts over half the banh xeo, fold over other half to cover filling, then slide onto serving plate and keep warm. Repeat with remaining oil, batter and filling, wiping pan with absorbent paper between batches, and serve with lettuce, herbs and nuoc cham.
The way to enjoy this would be to cut the banh xeo into smaller pieces, and place a bit of everything along with the herbs onto a piece to lettuce, dip in the Nuoc Cham and then eat with your hands!