Combine sugar, 1/2 teaspoon cornstarch, soy sauce, pork, and shrimp in a bowl and stir. Set aside.
In a bowl, rehydrate shitake mushrooms in hot water just enough to cover until softened. Depending on mushrooms used this can take anywhere between 15-30 minutes to soften. Reserve the liquid for dissolving cornstarch. Cut off the stem and cut into very thin match stick pieces.
In a small cup dissolve 1 1/2 T cornstarch with 3 T of reserved mushroom soaking liquid. This will be used to thicken the filling mixture.
Heat 1 1/2 T oil in a large skillet over medium high heat and add ginger and garlic. Cook for about 30 seconds until fragrant but not browned and add pork and shrimp mixture. Stir constantly to separate the pork pieces and shrimp into nuggets and cook for about 2 minutes. Do not overcook. Transfer to a dish.
Add the remaining 1 1/2 T oil to the skillet on medium high heat. Add shitake mushrooms, bamboo shoots, bean sprouts, salt and pepper. Cook 5 minutes stirring constantly. Return the pork and shrimp mixture to the skillet and stir to combine. Lower the heat and give the cornstarch mixture a stir and pour over the filling. Cook for about 30 seconds to bind the mixture. Transfer to a bowl to cool completely.
In a small cup combine 1 T cornstarch with 1/2 C water to seal spring roll skin.
Lay a spring roll skin on the work surface making sure one of the pointy corner is facing you. Put about 2 T of filling slightly below the center towards you and form into log shape using your fingers.
Lift the bottom edge towards you up and over the filling tucking the point under it. Fold in the sides and brush the upper edges with cornstarch and water mixture. Roll away from you (bottom up) to seal. Set the finished rolls seam side down on the baking sheet covered with wax paper or aluminum foil and keep covered with a kitchen towel to prevent drying.
Heat 1 inch of oil in a deep skillet over medium high to about 350F degrees. Slide in a few spring rolls and fry, turning as needed for about 3 minutes or until golden brown and very crisp.
Remove from the oil and drain. Continue with the remaining rolls. To serve, cut diagonally in half. Serve with a vinegar or dipping sauce of your choice.