Trim the base of the shimeji mushrooms and separate into small clusters. Slice the king oyster mushroom lengthwise into thin pieces. Separate the maitake mushrooms into small clusters. Thinly slice the garlic and remove its core.

Cut the bacon into 1cm wide strips.

Boil a large pot of water, add salt (not listed in ingredients), and cook the spaghetti 1 minute less than the package instructions. Reserve 5 tbsp of pasta water before draining.

Heat olive oil, garlic, and chili flakes in a frying pan over medium heat until fragrant. Add bacon, shimeji, king oyster, and maitake mushrooms. Stir-fry until the mushrooms soften.