Leek Flamiche - SippitySup

Ingredients

• chilled pastry dough (enough for a double-crusted tart, divided into 2 discs)
• all-purpose flour (as needed for rolling)
• 2 tablespoon unsalted butter
• 4–5 leeks (white and light green parts, thinly sliced, about 1 pound after slicing)
• kosher salt and white pepper
• 8 ounce semisoft cow’s‑milk cheese (such as Port Salut, Morbier, or even fontina, grated)
• 1 large egg (lightly beaten)
• 1 egg yolk (lightly beaten)
• ¼ cup half and half (plus more for brushing)