Prepare the Wrappers: Peel apart the individual sheets and cover with a damp towel to keep from drying out.

Prepare the Filling: In a large mixing bowl, combine the ground meat, onion, carrot, green onions, water chestnuts, egg, soy sauce, salt, pepper and onion powder. To test for adequate seasoning, fry a spoonful of the meat mixture and taste. Adjust seasonings accordingly by adding more salt, pepper, soy sauce and/or onion powder.

Wrap the Lumpia: Arrange 1 - 2 tablespoons of the meat mixture in a long strip almost near the middle of a wrapper. Fold one edge over the meat mixture and pinch to wrap the wrapper tight along the strip of meat. Fold each side over towards the middle and roll carefully, as tightly as possible, brushing the edge of the wrapper with water and pressing to seal the lumpia. Transfer to a plate and repeat until you've used up all the meat mixture and wrappers. Each lumpia will be roughly 5 1/2 inches long and about one inch in diameter.

Freeze for Later: Freeze the uncooked lumpia in a single layer in a storage bag. They will keep for weeks.

Fry the Lumpia: In a skillet, add enough avocado oil (or other neutral oil) to cover the lumpia halfway up. Heat to medium-high heat. Cook the frozen lumpia in batches (do not defrost first), flipping halfway through the cook time, about 5 - 7 minutes. Do not crowd the skillet and be careful not to overheat the oil to the point of smoking. The lumpia will burn outside and be raw inside. You want a light to medium golden brown color and a crispy exterior. Enjoy warm or at room temperature with sweet and sour sauce (sweet chili sauce or regular ketchup would work too). (Note: the cook time here is for each batch in the skillet, about seven pieces. The total cooking time will depend on the number of lumpia you cook.)