Put a well salted pot of water on to boil for the pasta.
Heat another wide bottomed pot and add 2 Tablespoons of olive oil and the chopped onion and garlic. Soften the onion then add the chopped broccoli and mushrooms. Season with salt and pepper and toss without colouring till heated through.
Add the stock and put the lid on and let the vegetables cook till just soft. Take off the heat and cool.
Put the broccolli in a food processor with the parsley, pine nuts, garlic, parmesan, 1/2 the lemon juice and zest and 1/2 of the olive oil. Blitz this mixture to break up a little.
This mixture doesn't need to be a puree so pulse it to keep texture.
Put the pesto into skillet or frypan and add the pasta water and cream. Add the pesto and more lemon juice and salt and pepper.extra seasoning. Drain the pasta saving a 1/4 cup and add to the pesto. Mix well with tongs.
Serve the pasta with extra parmesan Add more whole pinenuts if you want a crunchy texture