Peel and dice the onions and cook in butter on a medium heat until soft and without colour.

Add the brandy and cook for one more minute.

Add the flour to form a silky dough (roux).

Slowley add warmed milk a little at a time wile mixing to ensure no lumps.

Once all the milk is added, continue cooking slowley, whilst still mixing to cook out the taste of the flour. This is very important, do not turn up the heat at anytime.

Add the cheese, mustards and lea & perrins and season with salt and pepper.

Cool slightly and spread on one side of lightly toasted sourdough.

Return to the grill and cook until bubbly, and of an even colour.

Voila!