Hashbrown Crust Quiche with Leeks, Gruyère & Chive Oil

Ingredients

• 1 1/2 pounds russet potatoes (peeled or well scrubbed)
• 2 tablespoons olive oil or melted butter
• 1/2 teaspoon sea salt
• 1/2 cup Parmesan (finely grated, optional)
• 2 tablespoons unsalted butter
• 2 large leeks (white and light green parts only, thinly sliced)
• 6 large eggs
• 1/2 cup heavy cream
• 1 teaspoon Dijon mustard
• 1/4 teaspoon black pepper (freshly ground)
• 1 1/4 cups Gruyère (grated)
• 2 tablespoons fresh chives (finely chopped)
• chive oil (for drizzling)
• flaky salt
• extra chives (optional)