Soak wooden skewers in water for 20 mins.
Combine the saké, mirin, soy sauce and sugar in a saucepan, bring up to a boil, then simmer for 5 mins until slightly reduced. Cool.
Clean the mushrooms and remove the stems. Thread onto the skewers.
Heat a barbecue to a medium-low heat, brush the tops of mushroom with the glaze and cook for 2 mins.
Brush some of the glaze on the gills, flip over and cook for another 2 mins, repeat until cooked.
Put on a platter, brush with glaze, scatter with sesame seeds (or furikake) and spring onion.
¼ cup saké
¼ cup mirin
¼ cup soy sauce
2 teaspoons sugar
1 tablespoon sesame seeds (or Japanese seasoning furikake if you have it)
1 spring onion
thinly sliced 6 skewers (wooden or metal)