Pre-heat the oven to 350 °F.
Slice the cheese into 4 slices.
Quarter the tomatoes and remove the seeds. Chop the flesh into cubes. Toast the sliced bread in the toaster and place on a cookie sheet. Take two slices of cheese and put them on the bread and top with a slice of ham.
Divide the tomato, green onion and basil evenly among the two open face sandwiches and top with the remaining cheese slices. Put the cookie sheet in the oven and bake the sandwiches for 8-10 minutes until they are golden brown and the cheese is melted.
Put each open face sandwich on a plate. TIP
Try using Beemster Wasabi instead of Beemster Mustard and substitute the ham with sliced roasted chicken.