Preheat to 400 degrees F. Thinly slice the raw potatoes.
Slice the white nParboil the white baby potatoes slices for a few minutes or until tender, remove and set aside on a paper towel. Repeat the process for the purple potato slices.
Flour a surface. Roll out a sheet of puff pastry.
Using a ruler, trim the pastry into a square.
Transfer to a baking sheet with parchment paper.
Score the dough about 1 inch from the edge.
Using a fork, pierce the inside of the scored square.
Bake the shell for about 10 minutes.
Use a sharp knife to thinly slice potatoes
Grate about 1/2 cup cheese.
Take the pastry shell out of the oven and add the shredded gruyere.
Arrange the potato slices so that they alternate white and purple pattern.
Brush with olive oil and sprinkle sea salt.
Bake for 15-20 min.