1 preheat oven to 200C

2 melt butter in small saucepan over low heat and add the flour, stirring with wooden spoon for 1min to make roux

3 slowly add milk to roux, whisking constantly until sauce thickens

4 remove from heat and add nutmeg, Gruyere and parmesan and season

5 place bread on baking trays and bake for 3-4min

6 turn and toast for another 2min or until golden brown

7 spread each slice with mustand (or butter if not using mustard), add slice of ham, top with another slice of toast, then another slice of ham and another slice of toast then another slice of ham and final slice of toast

8 spoon about 3-4 tbsp of cheese sauce onto top of each toast stack and place under grill for 3min until golden and bubbling

9 remove from heat, serve hot