Napolitan (Japanese Ketchup Spaghetti)

Bahan-bahan (2 porsi)

• ⅓ cup ketchup
• ½ Tbsp milk ((optional; for a creamier taste))
• 2 tsp Worcestershire sauce
• 1 tsp sugar ((optional; for an authentic Japanese taste))
• ½ onion ((3.5 oz, 100 g))
• ¼ –½ green bell pepper ((2.5 oz, 70 g))
• 4 mushrooms ((2.5 oz, 70 g))
• 5 oz sausages
• 1 Tbsp extra virgin olive oil
• 1 clove garlic
• ¼ tsp Diamond Crystal kosher salt
• ⅛ tsp freshly ground black pepper
• 7 oz spaghetti
• 1½ Tbsp Diamond Crystal kosher salt
• ¼ cup reserved pasta water ((you may not need it; check your sauce and add gradually))
• 1 Tbsp unsalted butter
• 2 Tbsp Parmigiano-Reggiano or Parmesan cheese