In a microwave safe dish, add butter. Melt in 45 second intervals until melted. Add in garlic powder, onion powder, parsley and salt. Stir to combine. Place in refrigerator for 5 minutes.
Line two large baking sheets with parchment paper and place baking rack on each. Line out 12 slices of bread (6 on each sheet).
Remove butter mixture from the fridge and brush onto one side of each slice of bread. Lightly sprinkle with parmesan cheese. Then flip each slice so that it is is butter side down. Add a slice of cheese to each slice. Again, lightly sprinkle with parmesan cheese. Then add another slice of cheese to each. Top with second slice of bread.
Brush the top of each slice with butter mixture and lightly sprinkle with parmesan cheese.
Place both baking sheets in the oven. Bake for five minutes (DO NOT OPEN THE OVEN!!) then reduce heat to 350degF. Bake another 10 minutes.