Add the cubes of butter and cut them into the flour with a fork or your fingers until coarse.
½ cup cold butter
Add the egg and 2 tablespoons cold water and work the mixture together just until it forms a ball (you can add 1 more tablespoon cold water if needed). Flatten into a disc, cover with plastic wrap and chill for 30 minutes.
Preheat oven to 425°F and line a baking sheet or pizza pan with parchment paper. Slice the potatoes with a mandoline to make very thin slices.
2 medium Yukon gold potatoes
Mix sliced potatoes in a bowl with pesto sauce. Every slice should be coated with the sauce. Set aside.
½ cup basil pesto
On a lightly floured surface, roll out the dough into a circle that is approximately 13”-14” in diameter. Transfer to the parchment-lined pan.
Layer the potato slices starting from the center of the pastry circle, leaving a 2” border around the edge. Sprinkle with some salt and pepper.
Fold the dough border up around the edges to partially enclose the potato filling. The center will remain open.
Cover with aluminum foil and bake for 25 minutes. Remove the foil and bake for another 15 to 20 minutes or until the crust is golden brown and the potatoes are cooked. Remove from the oven and let it cool a bit.
Sprinkle with some freshly grated Parmesan cheese. Slice and serve.
Notes
Keep the galette refrigerated in an airtight container for up to 5 days.
It can be reheated in the oven at 350°F for 10 to 15 minutes.