Miso Butter Mushrooms in Foil

Bahan-bahan (4 porsi)

• 2 Tbsp miso
• 2 Tbsp sake
• ½ onion ((3.5 oz, 100 g))
• 4 shiitake mushrooms ((3 oz, 85 g))
• 1 package shimeji (brown beech) mushrooms ((3.5 oz, 100 g))
• 1 package maitake mushrooms ((3.5 oz, 100 g))
• 1 package enoki mushrooms ((3 oz, 85 g))
• 2 pieces king oyster mushrooms (eringi) ((4 oz, 113 g))
• 1 Tbsp unsalted butter ((for aluminum foil; divided))
• 2 Tbsp unsalted butter ((for topping; divided))
• 1 Tbsp soy sauce ((divided))
• chives ((optional; or green onion))