Trim and quarter the fennel and cook it in boiling salted water for about 30 minutes. When it is cooked, squeeze the pieces in a tea towel to extract the water.
Sieve the two hard-boiled egg yolks and the fennel into a large bowl with a mouli-légumes. Purée it thoroughly and scrape any bits which have stuck to the blade into the bowl. Add the mustard, lemon juice, salt and 2–3 turns of the peppermill to this purée. Whisk thoroughly and then whisk in the olive oil slowly as if you were making mayonnaise.
Put the cream together with the Pernod in a smaller bowl, and whisk until the cream thickens, then fold the cream into the fennel mixture in the large bowl. Taste the mixture and add salt, pepper and, if you like, a little more lemon juice.