Peel off one egg roll wrapper and place on a flat surface so that the corners are oriented north, south, east, and west.
Imagining an east-west line running across the center of the wrapper, place 1 heaping tablespoon of mung bean filling just below this centerline, in the middle of east and west.
Spread the filling out to about 4 inches across.
Place 1 tablespoon of mushroom mixture on top of the beans.
Spread the mushroom mixture evenly across the beans.
Fold the east corner 2/3 of the way toward the west corner.
Fold the west corner 2/3 of the way toward the east corner.
Take the south corner and fold it up ½ of the way toward the north corner. The crease of this fold should run right along the edge of the line of filling.
Roll the portion with the filling up toward the north corner.
Roll until you get a tube-shaped egg roll.
Set aside.
Repeat steps 1 – 6.
Add enough oil to a heavy-bottomed skillet so that oil depth is about ½ inch deep.
A cast-iron Dutch oven works well, too. Place over medium-high heat until oil shimmers.
Working carefully, transfer egg rolls to the oil, making sure to place them flap-side down to keep the rolls from opening up.
Add as many egg rolls as the skillet can hold without crowding. You want some wiggle room to be able to get in there and turn them over.
Let egg rolls cook until the bottom side is deep golden brown, about one minute.
Using tongs, rotate them to allow the top sides to cook until deep golden brown, about one minute.
Once all sides of egg rolls are golden brown, remove from skillet and place on a wire rack lined with paper towels. Let cool for about 10 minutes.
Enjoy either plain or with a spread of lettuce greens and herbs.