Ch- Ch- Chef Changes… Sometimes, the local boy makes good. Chesterfield, Md.-native Nathan Beauchamp has picked up the knife to direct the nightly deliciousness that is tradition at 1789. He’s no stranger to the D.C. scene either, having worked at both Bistro Bis and Restaurant Eve, two of DCist’s favorites. According to the restaurant, the chef will unveil his new menu sometime in February. He’s giving a nod to old favorites such as the oyster…