Start by buttering one side of each side of the bread slices.
Slice the cheese and place evenly half of the cheese on each side of 4 bread slices. Place the ham on top. Place evenly the rest of the cheese on top of the ham slices. Place the rest of the bread slices with the buttered side on top of the cheese.
Place the bread on a baking paper on a baking sheet.
Preheat the oven at 225 degrees Celsius.
In a casserole whip together the milk, butter and the flour while stirring the whole time. When it reaches boiling point lower the heat and let it boil for 3 minutes.
Add the grated cheese and let it melt and mix well.
Pour evenly the sauce over the bread slices.
Place in the oven for 8- 10 minutes. Take out and serve warm.