Lightly toast the bread in the toaster (or under the grill). Butter the slices on one side and put the slices in a gratin dish in a single layer, buttered side up.
Put a slice of ham on each slice of toast, then put slices of Reblochon on top (use the whole cheese). Scatter over the breadcrumbs and parsley, then pour on the cream and season.
Put the dish in the oven and bake for 10-12 minutes. You’ll need to keep an eye on it and retrieve the dish before the cheese starts to completely lose its shape – it should be soft, but not running off the bread.