Cook pasta in salted boiling water until al dente. Reserve 100 ml of pasta water, then drain.

In a pan, heat butter and olive oil over medium-low heat.

Add leek, spring onions, and thyme. Cook gently for 5 minutes until softened (do not brown).

Place salmon fillets on top of the vegetables. Season with salt, pepper, and lemon zest and juice.

Cover and cook for 5 minutes, then flip salmon and cook for another 3 minutes.

Remove salmon and set aside.

Stir crème fraîche into the leek mixture, then add reserved pasta water gradually.

Bring to a gentle simmer and season to taste.

Add cooked pasta and toss to coat evenly.

Divide onto plates and flake salmon over the top. This Salmon Pasta is best served immediately.