Remove the roots and green leaves from the leek. Halve the trunk lengthwise, then cut both halves into half rings.
Cut the baby spinach into small pieces.
Finely chop two-thirds of the walnuts. Keep some aside for finishing.
Cut the Gorgonzola into coarse pieces.
Fry the leek rings with some oil in a deep pan.
After a few minutes, add the Gorgonzola and cream.
Mix everything well and let it reduce slightly. Season with salt, pepper and nutmeg.
A few minutes before serving, add the walnuts and spinach.
Meanwhile, cook the tagliatelle as indicated on the package. Fresh tagliatelle should only cook for a minute or two. If you use dried tagliatelle, it is recommended start cooking it before you make the sauce.
Serve the tagliatelle on plates with the sauce. Finish with some walnuts.