Nigel Barden served up simple cod gratin with Bearnaise sauce on Radio 2 Drivetime.

The ingredients are: 2 leeks, sliced, 2 carrots, sliced, 1 onion, chopped, 40g butter, plus extra for greasing, 600g cod loin, skinned and cut into 3cm chunks, 2 tbsp plain flour, 50ml dry white wine, salt and freshly ground black pepper.

For the béarnaise sauce: 70ml white wine vinegar, 2 shallots, finely chopped, 2 sprigs fresh tarragon, plus 1 tsp freshly chopped, 1 bay leaf, 6 peppercorns, 4 free-range egg yolks and 300g unsalted butter.