These hors d'oeuvres are flaky, chewy, and impossibly good with a chilled glass of Riesling. The palmier is a classic shape in French pastry that's easy to form and that shows off fillings beautifully. Here, I layer mustard, ham, and Gruyère cheese with the pastry, so the flavors are classic, too. Get the ham sliced very thinly at the deli counter. If the ham falls apart a bit, that's okay; you can piece it together as you assemble the palmiers.