leek and swiss chard tart

INGREDIENTS

• 1 sheet frozen puff pastry (half of 17.3-ounce package), thawed (I used a basic tartdough instead)
• 2 tablespoons (1/4 stick) butter
• 3 large leeks (white and pale green parts only), coarsely chopped
• 1 teaspoon dried thyme
• 1/2 bunch Swiss chard, ribs removed, leaves chopped (about 2 1/2 cups)
• 1 1/4 cups whipping cream (I used whole milk)
• 3 large eggs
• 2 large egg yolks
• 1 teaspoon salt
• 1/4 teaspoon ground black pepper
• Pinch of ground nutmeg