Remove the stems of 3 king oyster mushrooms and slice them evenly. Chop the green chili and spring onion into small pieces.

Mix 5 tbsp soy sauce, 2 tbsp oligosaccharide, 2 tbsp water, 1 tbsp minced garlic, and 1 tbsp sesame oil. Add the chopped green chili and spring onion to the mixture.

Heat a pan over medium-low heat and melt 1 tbsp butter. Grill the mushroom slices on both sides until golden.

Pour the prepared seasoning over the mushrooms, ensuring they are submerged. Simmer on low heat until the sauce thickens slightly.