Mix the prawns with 1 teaspoon salt. Set aside for 10 minutes. Rinse and drain the prawns. Set aside.
Cook the Sauce
In a large pot, heat a few lugs of olive oil over medium heat. When the oil is hot but not smoking, add in the onion and chilli - the onion should sizzle gently. Turn down the heat to low and cook the onion for 5 minutes, stirring frequently until the onion has softened and is translucent. Add in the garlic and continue to cook on low heat until the garlic is fragrant.
Push the onion-garlic mixture to the side of the pot. Turn the heat up to medium and add in a little bit more oil if the pot is dry. Sear the prawns on both sides until cooked through. Remove the prawns and set aside.
Add in the mushrooms and cook over medium-high heat until the mushrooms have softened and shrunk in size. Add in the water/stock, stock cube (if using) and bay leaf. Turn up the heat and bring it to a boil, then reduce the heat and simmer gently until the stock has reduced by 1/3, stirring frequently.
Cook Pasta
Meanwhile, bring a large pot of water to boil and season with salt (1/2 tablespoon salt per 1 litre of water). Add in the spaghetti and cook until al-dente.
You can incorporate incorporate vegetables (e.g. beans or peas) into the pasta - simply add them into the boiling water towards the end, depending on how long they take to cook.
Return to the Sauce and Add the Pasta
Stir in the cream and bring to a simmer (do not let it boil). Season with salt and black pepper to taste.
Drain the pasta and vegetables, reserving 1 cup of pasta water. Add the pasta and vegetables immediately into the cream sauce, tossing to coat the pasta. If the sauce is too dry, add in pasta water, bit by bit until you achieve your desired consistency. Adjust the seasonings, and add in the cooked prawns if desired, otherwise plate them separately.
Serve immediately!
NOTES
Adapted from Johnny's (Feed the Piglet) Prawn Pasta