1. Butter both sides of 16 slices of bread. Place 8 slices in a 8 x 25 cm pan 5 cm deep. Cover bread with sharp cheese and a slice of ham on each piece of bread. Top with the remaining 8 slices of bread.
2. Mix together all the rest of the ingredients except melted butter and cornflakes. Pour over casserole and refrigerate overnight.
3. Before baking, mix the melted butter and cornflakes. Spread evenly over casserole. Bake at 180ºC for 1 hour.