Method

• 1.
  Preheat the oven to 180°C.
• 2.
  Slice fennel in half lengthways, then toss with 1 tablespoon lemon juice to prevent discolouring. Bring a large pan of salted water to the boil. Add the fennel and reduce heat to medium, then simmer for 10-12 minutes until fennel is just tender.
• 3.
  Meanwhile, for the topping, combine the breadcrumbs, walnuts, thyme, parmesan, cream, garlic, fennel seeds, lemon zest, remaining lemon juice and reserved fennel fronds in a bowl. Season to taste.
• 4.
  Drain the fennel and place cut-side up in a shallow baking dish. Divide the topping mixture among the fennel bulbs.
• 5.
  Carefully pour the stock around the fennel, then loosely cover the pan with foil. Bake for 20 minutes, then remove the foil and return to the oven for a further 25-30 minutes until the gratin is golden.