Preheat oven to 375°F.
Place cranberries, sugar, water and rosemary in a pot with a pinch of salt. Bring to boil and cook berries to form a thickened sauce, about 15 minutes at a rapid simmer. Remove from heat.
In another small saucepot, melt butter. Whisk in flour and milk, and add crushed garlic if using; season with salt, pepper and nutmeg to taste. Stir in Parm.
Place bread slices out on a baking sheet and top with the white sauce, some sliced turkey and shredded Fontina or Gruyère. Transfer to oven and bake to golden.
Top with small handful of greens and eggs, if making Croque Madames. Serve additional sauce alongside.