To make this indulgent tasty lunch, firstly preheat the oven to 220C / gas mark 7.
In a pan, add onion, bay leaf, mace, salt and pepper to the milk – and simmer for 3-5mins. Remove from heat, then strain the milk and put aside.
Next, melt the butter in a separate pan over a medium heat, then add flour, stirring until a paste forms. Gradually, add the infused milk, stirring continuously until a smooth sauce forms (3-4mins). Remove from heat and allow to cool.
Place all bread slices on a baking sheet with greaseproof paper, and spread a thin layer of béchamel sauce on each one.
On one slice, top with a layer of ham and then a layer of cheese.
Add the other béchamel slice on top – béchamel facing up.
Sprinkle more cheese on top, then bake in oven until cheese has melted and the sandwich is golden in colour (10-15mins). Enjoy!