Rosemary Shrager served up a tasty lobster thermidor sauce for her students on Chopping Block.

The ingredients are: 25g flour, 30g butter, 1 shallot, finely chopped, fish stock, 55ml white wine, 100ml cream, ½ tsp mustard, ½ lemon, juice only, parsley, milk, Parmesan cheese, salt and pepper for seasoning.