Preheat oven to 375 degrees.
Peel potatoes and slice 1/4 inch thick. A mandolin works best for this. Peel onion and slice in 1/4 inch slices. Separate onion slices into rings.
Add potatoes to a medium sauce pan and cover with cold water. Slowly bring to a simmer and cook for 8 minutes. Drain potatoes in a colander.
In the meantime heat a fry pan over medium high heat. When hot, add neutral oil, such as safflower or sunflower oil to the pan. When oil is shimmering, add onions. Turn down heat and cook for about 10 minutes, until onions are starting to brown. Transfer to a paper towel when done.
To build packets, arrange rectangular pieces of parchment paper on counter. Place potatoes on the top half of the paper. Top with grated cheese, onions and 1 tablespoon cream for each pouch. Seal using method in this post.
Bake for about 30 minutes. To serve, simply tear open the pouch in the middle and plate.