• Gather all the ingredients.
  
• Bring a large pot of water to boil. Once boiling, add 2 Tbsp kosher salt and cook the spaghetti until al dente, about 10 minutes (check the package instructions as well).
  
  
• In a large bowl, combine 2 Tbsp milk, 2 Tbsp heavy whipping cream, 2 Tbsp unsalted butter, and 1 Tbsp soy sauce. Don't worry if the butter becomes solidify. Hot spaghetti will melt the butter again.
  
• Add freshly ground black pepper and stir to combine.
  
  
• Cut each roe sac in half and squeeze out the roe from the sac with hands or knife.
  
  
• Add the roe to the bowl and mix well. Discard the membrane.
  
  
• When the spaghetti is done, drain and transfer to the large bowl with the sauce.
  
  
• Toss to combine until the butter is melted and the sauce is evenly distributed. Taste and adjust with black pepper and kosher salt.
  
  
• Serve immediately, garnished with shredded nori. If you can find shiso leaves in a Japanese grocery store, roll them up and cut it into thin strips and garnish. Shiso is a wonderful addition to this dish.
  
  

To Store

• Unfortunately, you can't keep the leftovers. If you reheat mentaiko, the fish eggs will be cooked/overcooked.