3 T butter
4 slices of crusty white bread with crusts cut off
100ml milk
1 T plain flour
2 oz grated Gruyere
Dijon mustard
Good ham

Preheat grill. Line a tray with foil. Melt the butter.
Brush one side of bread with melted butter. Place under grill butter side up and cook until golden brown.

Stir flour into remaining butter, cook for a minute then whisk in milk until smooth. Simmer until thickens. Take off heat and add 1/3 of cheese.

Spread untoasted sides of bread with mustard. Place ham on top followed by cheese. But back until grill till cheese melts.

Put the halves together, press down. Cover with the bechamel sauce and place under grill again until golden and bubbling.