Gather all the ingredients.
If you are baking, preheat oven to 350If you are grilling, preheat grill to 350F.
Using the sheet of aluminum foil, make a pouch that measures around 10"x12". Place butter inside of aluminum pouch and set aside.
Cut off about 1 inch from the bottom of the Enoki mushroom and discard (this will get rid of the dirt). Wash Enoki mushroom thoroughly with water while trying to break apart the mushrooms as much as possible. Squeeze out any excess water with your hands and transfer the Enoki mushroom into the aluminum pouch on top of the butter.
Finely dice garlic cloves and place on top of Enoki mushroom, along with salt, black pepper and Japanese sake.
Close foil pouch while leaving about 7/8 gap open on top.
Finely chop green onions and set aside.
For grilling, place foil pouch on indirect fire (back of griland cook for 10 minute s with lid closed, maintaining a temperature of about 350Occasional stir the mushroom around to help mix in sauce and close back up. Once 10 minutes has passed, transfer to a serving plate, top with chopped green onions and enjoy hot! For baking, place foil pouch in the center of the oven and cook for 15 minutes. About halfway through at the 7 minute mark, stir the mushroom around to help mix in sauce and close back up. Once 15 minutes has passed, transfer to a serving plate, top with chopped green onions and enjoy hot!