Place the oyster mushrooms in a food processor and pulse until they resemble rice. Transfer them to a bow and set aside.
Without wiping out the processor bowl, add the spinach, garlic and scallion whites and pulse until finely chopped. Add these to the mushrooms.
Chop the kimchi finely and also add it to the bowl. Stir well to combine the mixture.
Heat a large pan on medium heat and add the sesame and peanut oil to heat for 30 seconds. Add the mushroom mixture and tamari sauce and cook, stirring regularly for 3 to 5 minutes. Remove the mixture from the heat to cool well. You can also refrigerate the mixture prior to making the dumplings to help with binding but I don't always and it's fine.
To make the dumplings, place a small bowl of water and a parchment-lined baking sheet near your workspace. Lay several dumpling wrappers on your bench and place a heaped teaspoon of the filling in the middle of each wrapper. Dip a finger in the water and run it around the edge of the first dumpling wrapper. Fold the wrapper over and pinch it closed. If the wrapper opens again, pinch it together again with wet fingers. I also pleat mine to ensure they seal properly. Repeat with remaining wrappers until all the filling is used.
If freezing, lay the dumplings as closely as possible on the baking sheet without touching. Freeze until solid before transferring them to a freezer-proof container and freezing for up to three months. Dumplings can be cooked straight from the freezer without thawing.
To boil the dumplings, fill a large pot with water and bring to the boil over medium heat. Add your dumplings and cook for around 5 minutes, stirring occasionally to ensure they don't stick to the bottom of the pot. When the dumplings rise to the surface of the water, they are ready. Strain and serve with freshly chopped scallions and a soy chilli sauce.
To pan-fry the dumplings, heat vegetable or grapeseed oil in a large skillet over medium heat. Add the dumplings and gently fry each side until golden. Remove from the pan and serve with freshly chopped scallions and a soy chilli sauce.