Mince the garlic, put it in big bowl and add olive oil mix. Chop 1 tbsp of fresh thyme, add to the bowl and stir. Set aside.
Heat a pan to medium. Cook the prosciutto till it gets crispy crispy then remove from heat and chop in small chucks like bacon bits once it has cooled. Dice the onions, add them to the same pan as the prosciutto and sauté till tender.
Meanwhile, peel the potatoes and yams. With a mandolin, slice the potatoes and yams 1/4" thick. Place the yams and potatoes in the garlic mixture and coat really well with.
Spray a muffin tin with non-stick spray. Place a potato slice on the bottom of the all the spots in the muffin tin. Then place a yam on top of the potato. Next, sprinkle about 1 tsp of onion and 1 tsp of prosciutto then 1/2 to 1 tsp parmesan cheese. Repeat until you have filled the muffin tin to the top of the tin. Finish with any kind of potato and then add some parmesan cheese on top. You can layer above the muffin tin because the stacks will shrink a little.
Bake for 40 min or till potatoes are fork tender. Serve right out of the oven.