Preheat the oven to 425.

Lightly flour your work surface. Unfurl the thawed puff pastry and lightly roll it out to about the dimensions of your baking sheet (just slightly less than so it fits).

Transfer the rolled out puff to a parchment lined baking sheet. Using the tip of a knife, score a ½” border all around the edges (don’t cut all the way through!). Lightly poke the dough with a fork, all over the surface area. Transfer to the fridge to chill while you prepare the potatoes.

Using a mandoline, thinly slice 2 large russet potatoes about ⅛” thick. In a medium bowl combine the potatoes and ¼ cup of olive oil. Season with salt and pepper and toss well to combine.

Working in straight rows, shingle the potatoes (about 10 per row) on top of the pastry, allowing them to overlap and making sure they don’t surpass the scored edge. Repeat with all the potatoes until the entire pastry has been covered twice over (meaning, you’ll have two layers of potatoes across the whole tart. Work quickly here so the puff doesn’t warm too much! Just before it goes in the oven, lightly brush the tops of the potatoes with one more tablespoon of olive oil.

Bake, rotating the baking sheet halfway through until the outside edges of the potatoes are crisp and golden brown (the interior ones will still be yellow and soft) and the puff pastry has puffed and turned golden, 45-55 minutes. Let cool at least 10 minutes.

Finely grate the zest of 1 lemon over the tart. Season the tart with flaky sea salt.

Dollop the tart with small spoonfuls of sour cream.

Tear 4 ounces of smoked salmon into bite sized pieces and arrange over the tart.

Thinly slice ½ bunch chives and/or pick the leaves of ¼ cup dill (depending on which you are using). Scatter over the tart.

Dollop small spoonfuls of caviar or salmon roe over the tart, if using.

Squeeze the juice of the lemon over the whole tart. Cut into squares and serve.