Gather all the ingredients.
In the meantime, line oven tray with aluminum foil and lightly spray cooking oil or use a silicone baking mat. Preheat oven to 400F.
Cut 1 tbsp of cream cheese into 1/4s, so each tbsp will yield 4 cubes. You should end up with 12 cubes. Each dumpling will need 1 cube, so you may need more or less depending on your exact batch size.
Soak dried shiitake mushroom in warm water until softens,should be about 5-10 minutes. De-stem, dice mushrooms and add to mixing bowl along with diced cabbage leaves, grated garlic, chopped green onions, ground pork, toasted sesame oil, soy sauce, half & half, egg, Japanese sake, panko, salt and black pepper.
Take a small amount of dumpling mix and make a patty, place the cream cheese on top, and softly cup the edges of the patty to form a ball and place on the oven tray. Each ball should around the size of a golf ball and you should end up with around 10-14 dumplings.
Place the oven tray in the center of the oven and cook for 18-20 minutes (internal temp with meat thermometer should be 160F). Transfer to serving plate when done.
Optional Sauce - you can eat these dumplings without any dipping sauces, but if you prefer sauce, simply mix soy sauce and white vinegar.