Summary: Leek & Goat Cheese Tart With Cabernet OnionsMakes two 11½-by-8-inch rectangular tarts6 tablespoons unsalted butter, divided4 large leeks, white and pale green portion, diced (about 5 cups)Kosher salt and freshly ground black pepper to taste4 medium yellow onions, peeled and cut into ½-inch thick rings3 cups Cabernet SauvignonMelted butter or pan spray for greasing the tart panAll-purpose flour as needed2 sheets puff pastry dough, defrosted according to package instructions1 cup whole milk1 cup heavy whipping cream4 large eggs2 large egg yolks1 cup...
