Gather your ingredients. Preheat oven to 425 degrees. Line a baking sheet with parchment paper.
Cut your potatoes into 1.5" squares and place them into a large pot.
Cover the potatoes with cold water and add some salt. Bring to a boil and then reduce heat to a simmer. Cover pot and cook for about 15 minutes.
Remove the potatoes from water when they are nearly falling apart with a fork.
Melt butter over medium heat. Add the garlic and sauté until softened.
Remove from heat and stir in the cream. Set aside.
Put your potatoes through a ricer (or mash them well in a bowl).
Mix the garlic butter into the potatoes. Add the parmesan. Stir well.
Slowly add in your egg yolks while stirring. Be sure the potatoes aren't so hot as to solidify the egg. Add additional cream if the mix is too thick.
Using a piping bag (or other apparatus as you see fit), create and form the potatoes into your desired size & shape on a baking sheet lined with parchment paper.
Place into the oven for up to 30 minutes. Keep an eye on them though as they may be done sooner.
Remove when the potatoes have formed a nice brown crust. Optional – Lightly brush with truffle oil.
Serve & Enjoy!