Preheat oven to 400 degrees. Cut off the ends of the sweet potatoes. Slice sweet potatoes into 4-6 thick slices and place on two baking sheets.
Brush olive oil on each slice. Sprinkle with salt and pepper. Place both baking sheets into a preheated oven and bake for 35-40 minutes until soft. Make sure to rotate the sheets halfway through baking so that they bake evenly.
While the potatoes are baking, mix melted butter, chopped parsley, and garlic in a small bowl with a spoon. Set aside.
Once the potatoes are cooked through, remove baking sheets from the oven. Using two forks smash the sweet potato down so that it mashes and flattens. If you break the shape of the round, just reshape it into a circle with your forks.
Spoon a small amount of the butter mixture onto each round and spread with the back of the spoon. Do not add too much; the garlic packs lots of flavor so you only need a small amount of the mixture per round, about 1/4 teaspoon. Place buttered rounds back into the oven for 15 more minutes, or until skins get crispy.
Once the rounds have crisped up, remove from oven and immediately sprinkle shredded/grated Parmesan on top. Let them cool for 5 minutes and then serve.