Heat oven to 350.
Lay cheese slices on parchment-lined baking sheet, leaving space around each slice. Bake until melted and bubbly. Remove from oven.
Sautee onions, mushrooms and ground meat in a frying pan until beef is cooked through. Add ginger, garlic, tamari, salt and pepper. Allow to cool slightly.
Put 1-2 tbsp of the meat mixture in one corner of each slice of cheese.
Fold corner of cheese over the meat mixture and press edges together. They will not seal yet, but just fold as best you can.
Place back in oven for another minute or 2 until the edges have sealed.
Serve with salad or crudite.