Hi Constance,
Such a good question for parties anytime of year, and even more so as the winter holidays approach.
Ideally, prepare the appetizers ahead, place on a baking sheet, loosely cover with plastic wrap, and refrigerate until ready to bake, then pop in the oven shortly before serving. You'll have optimal puff and crispness.
That being said...yes, you can keep baked pastries warm in a warming oven. I would advise the following: bake the pastries an hour ahead, but then take them out of the oven and place on a cooling rack (to stop the cooking/prevent over-browning). Let cool to room temperature. Then, loosely cover with a large sheet of foil and place in the warming oven on the lowest temp (200F) until ready to serve.
Don't leave them in there too long, or they will dry out. I do not have a maximum time, but I would not keep them in the warming oven longer than 20-30 minutes.
Camilla
