Boil a large pot of water and cook the spaghetti noodles according to the package's instructions. Reserve pasta water, then drain noodles. Stir together pasta water & dashi powder, then set aside.

Add butter & onions. Cook for about 10 minutes, or until golden and caramelized, stirring occasionally. Add garlic, sauté for a few seconds until soft and fragrant. Then pour in soy sauce along the edges of the pan to create a char then stir to combine.

Pour sake and stir to deglaze any browned bits from the pan. Cook for about a minute until the alcohol has evaporated.

Pour in dashi pasta water, stir, then cook until the stock has reduced by half, stirring occasionally.

Add miso paste and stir until dissolved. Add heavy cream and parmesan cheese. Stir and cook until the cheese has melted. Reduce the heat if needed so the sauce doesn't come to a boil, otherwise, your sauce may have a grainy texture. Taste & adjust seasonings if needed.

Add pasta to the sauce and stir until well combined. Turn off heat, spritz with lemon juice, give it a final toss, then transfer to a serving plate. If you’re feeling fancy, garnish with extra grated parmesan and furikake, shredded nori, or chives. Enjoy!