Peel the bottom half of the asparagus and cut into 4cm diagonal pieces. Separate the shimeji mushrooms into small clusters. Tear the prosciutto into bite-sized pieces.

Boil water in a pot, add a pinch of salt (not listed in ingredients), and cook the spaghetti according to package instructions. Reserve 50ml of pasta water before draining.

Heat olive oil in a frying pan and sauté the asparagus and shimeji mushrooms briefly.

Add the prosciutto, reserved pasta water, and sauce ingredients (heavy cream, lemon juice, salt, butter) to the pan. Bring to a boil, then add the cooked spaghetti and toss to combine.