To make the batter, combine rice flour, cornstarch, turmeric, and salt in a bowl. Whisk in coconut cream and water. Stir in the green scallion. Set aside to rest for 1 hour.
To make the dipping sauce, combine everything in a bowl and whisk together until combined. Set aside until ready to serve.
Wash and drain the pre-soaked mung bean. Put the mung bean in a steamer and steam for 15 minutes or until mung bean is soft. Set aside.
Add a tablespoon of oil to the pan over med-high heat. Add the portioned prawns and pork and cook until pork browned and prawns opaque, about 1 minute. Separate the mixture on two opposite sides of the pan leaving a border in the middle.
Ladle 1/3 cup of batter into the pan, swirl to cover the pan and fillings. Add a little bit of batter to fill the empty spots.
Sprinkle 2 tablespoons of cooked mung bean all over the pan. Add 1/2 cup of bean sprouts to one side of the pan.
Cover the pan with a lid and cook for 3 minutes until everything is cooked through.
Uncover the lid, drizzle 1 tablespoon of oil around the edges and cook for another minute until the bottom and edges are crispy.
Slide a spatula under one side and fold crepe over to cover the fillings. Transfer the folded crepe to a plate.
Slide finished crepe onto prepared rack and place in oven to keep warm at 225 degrees F while you make the remaining crepes.
Repeat with remaining oil, batter and fillings for 5 more crepes, wiping the pan with absorbent paper between batches.
Serve the crepes immediately with mustard green, lettuce, herbs and nuoc cham.