Cook the Pasta: Bring a large pot of water to a rolling boil. Add a very generous amount of salt (it should taste like the sea). Add the spaghetti and cook according to package directions until al dente. This usually takes around 8-10 minutes.

Start the Sauce: While the pasta is cooking, place a large, wide frying pan or skillet over a low-medium heat. Add the olive oil and the cubed butter. Let the butter melt gently.

Infuse the Garlic: Add the thinly sliced garlic and the red chilli flakes (if using) to the melted butter. Cook gently for 2-3 minutes, swirling the pan often. We are looking to soften the garlic and infuse the butter with its flavour, not to brown it. It should become fragrant and pale golden.

Reserve the Magic Water: Just before you drain the pasta, scoop out at least 300ml of the starchy cooking water and set it aside. This is the crucial ingredient for creating a silky sauce.

Combine Pasta and Sauce: Drain the pasta (don't rinse it!) and immediately add it directly to the pan with the garlic butter. Use tongs to toss everything together so the pasta is well coated.

Create the Emulsion: Pour about 200ml of the reserved pasta water into the pan. Increase the heat to medium and toss the pasta continuously for 2-3 minutes. You will see the water and butter come together to form a creamy, glossy sauce that clings to the pasta. I find that vigorously tossing and stirring is what really helps the sauce emulsify.

Add the Finishings: Remove the pan from the heat. Add the grated Parmesan cheese, the chopped parsley, and the fresh lemon juice. Season generously with black pepper and a little salt if needed (the pasta water and cheese are already salty).

Serve Immediately: Toss everything one last time until the cheese is melted and everything is beautifully combined. Serve straight away in warm bowls with an extra grating of Parmesan on top.