Preheat oven to 180C.

For mornay sauce, heat butter in a saucepan over medium-high heat and sweat the onion and garlic until softened. Add flour and stir continuously until flour begins to turn sand-coloured, for another 2-3 minutes. Gradually add milk, stirring well between each addition, until incorporated and sauce is smooth. Stir in the mustard and cheese, season well to taste and stir in herbs.

Bring a very large saucepan of salted water to the boil. Boil lobsters until half-cooked (4 minutes). Drain, then using a sharp knife and kitchen scissors, split lobsters in half. Remove meat from tails and legs (leave head and tail shell intact), coarsely chop tail meat and transfer to a bowl. Set shells and meat aside separately until required.

Combine half the mornay sauce with the lobster meat and stir to combine, then spoon mixture into shells in a baking dish, spoon extra sauce over to cover well, then bake in the oven until mornay turns golden and bubbly (20-30 minutes).

Season to taste and serve hot with lemon wedges and a leaf salad.