Haidar Karoum is a busy man. Over the past five years, the northern Virginia native has opened three popular restaurants in Washington, D.C. And when Karoum isn’t crouched over the hot stoves at Proof, Estadio, or Doi Moi, he’s traveling the world in search of culinary inspiration—particularly for the latter two restaurants, a tapas joint and a pan-Asian spot. This time of year, however, Karoum is just as susceptible to the charms of the soft-shell crab as any other chef in D.C. At Doi Moi, he brushes softies with scallion oil, grills them, and plates them with a simple Vietnamese dip that brings welcome hits of salt, heat, and citrus to the table.