Alsatian Potato Pie - SippitySup

Ingredients

• 3 (about 1 ½ pounds) yukon gold potatoes, peeled and cut into ¼‑inch-thick rounds
• 1 pinch coatse salt, plus more as needed
• 5 cloves garlic, crushed with the flat side of a large knife
• ½ teaspoon freshly grated nutmeg
• 1 pinch frshly ground black pepper
• 2 tablespoons unsalted butter
• 1 medium leek, white and light-green parts only, halved lengthwise, thinly sliced crosswise, and washed well
• ¼ cup chopped fresh flat-leaf parsley
• 1 large egg yolk
• 1 (14 ounces) frozen puff pastry, (such as dufour), thawed
• unknown all purpose flour, for dusting work surface
• 1½ cup grated comte or gruyere cheese