House & Home - Leek and Brie Galette

Ingredients

• 1 medium lemon
• 3/4 cup all-purpose flour
• ½ cup rye or whole-wheat flour
• Kosher salt
• ½ cup unsalted butter, chilled
• ¼ cup plain yogurt or sour cream
• ¼ cup cold water
• 2–3 large leeks
• 2 tbsp olive oil
• Freshly ground black pepper
• 1 large garlic clove, minced or finely grated
• 1 tbsp smooth Dijon mustard
• 4 oz. brie, cold, sliced ¼” thick
• 1 egg, lightly beaten (optional)