Cook the pasta in a large pan of boiling salted water according to the packet instructions.
Meanwhile, deseed and finely chop the chilli. Melt the butter with a little oil in a frying pan while you bash the fennel seeds using a pestle and mortar till ground.
Add the fennel to the pan with the chilli and fry for 1 minute, then add the crab to heat through. Once done, remove from the heat.
Using a peeler, shred your asparagus into long thin strips and leave to one side.
When the pasta is done, drain, reserving a cup of the pasta water and add the pasta to the frying pan with the crab.
Place back on a medium heat, add the asparagus, the zest and juice of the lemon and toss well, adding a little pasta water to loosen.
Season to taste, then serve with a drizzle of oil, topped with pea shoots or rocket.