Finely mince the shrimp until it forms a paste-like consistency.
In a large bowl, combine the ground pork, minced shrimp, tamari, toasted sesame oil, grated ginger, minced garlic, sliced green onions, sea salt, and black pepper.
Mix the filling thoroughly with your hands until the mixture becomes slightly tacky and well-incorporated.
Place a wonton wrapper in the palm of your hand and add about one tablespoon of the filling to the center.
Gently squeeze the sides of the wrapper upward around the filling, leaving the top open and flattening the bottom so the dumpling can stand upright.
Line a steamer basket with cabbage leaves to prevent sticking and arrange the shumai inside, ensuring they do not touch.
Steam over boiling water for 8 to 10 minutes until the pork is cooked through and the wrappers are translucent.
Serve warm with extra tamari or a splash of rice vinegar if desired.