In a wok or skillet, saute garlic and onion in oil over medium heat until limp. Add the ground pork and cook for 3 minutes stirring constantly to remove lumps. Next, add the tofu and cook for 3 minutes or until edges are lightly golden. Add the prawns and cook until it turns pink all over.
Add the sweet potato, carrots, and water. Let it cook for another 3 minutes or until the sweet potatoes are just cooked. Add the cabbage and fish sauce. Season with salt and pepper as needed and cook for a few minutes more just until the cabbage is done.
Transfer to a colander to remove excess liquids if any. Let it cool down a bit. Meanwhile. prepare the wrappers and sauce.
In a bowl, combine all the dry ingredients for the wrapper. Add a quarter of the milk and whisk to make a paste. This is to prevent lumps from forming. Then add the rest of the ingredients while whisking continuously. Run the runny batter into a sieve to have a smoother batter and later smoother wrappers.
Heat a non-stick crepe pan over low heat. Spray or brush the pan with a little amount of oil. Pour half a cup of batter into the pan and immediately tilt from side to side in a circular motion to cover the bottom with the batter. Cook for 2-3 minutes or until the batter is no longer liquid and no longer sticks to the pan. Do not let it turn brown. You may need to flip it over but as long as the top has also dried out, then no need. Transfer wrapper to a plate and set aside.
Now to prepare the sauce. Just combine all the ingredients, except the cornstarch mixture in a saucepan and bring it to a soft boil over medium-low heat. Let it cook for 3 minutes. Add the cornstarch mixture and cook while whisking constantly until the sauce becomes thick,
To assemble, place a wrapper on a plate or on a flat surface and place a lettuce leaf on top. Spoon some fillings across the middle half of the wrapper. Fold in the wrapper into the center starting from the bottom and then the sides cover filling.
Pour some sauce on top of the wrapped Lumpia then sprinkle with chopped peanuts.