Lay the puff pastry sheet in the pie pan together with its parchment paper underneath.
With a fork, punch holes in the pastry throughout the whole bottom of the pan, then crumble the goat cheese (or spread if it's soft enough) evenly in the center of the pastry.
Peel the sweet potatoes and cut them in ribbons using a peeler or a spiral slicer (see below for the one I used) and add them in a large bowl.
Season with a drizzle of olive oil, salt, black pepper, Cayenne pepper, thyme and oregano, then toss with your hands to coat evenly.
Shape the sweet potatoes ribbons as a rose in the pie pan, starting from the center and adding outer layers as petals.
In a bowl, whisk the 2 eggs with the sour cream and the Pecorino cheese and lightly season with salt and pepper.
Pour the mix on top of the potatoes. Most of it will drip down under the potatoes and will act as glue.
Bake in the oven for 25-30 minutes, or until the crust is golden brown.
Notes
You can substitute Pecorino Romano for the classic Parmigiano cheese. You can also chop the sweet potatoes into small cubes to have a more rustic looking Quiche.