Preheat oven to 400 degrees F.
Combine flour, baking powder, salt, and sugar in bowl of electric mixer fitted with the paddle attachment. Add butter and mix on low speed until butter is size of peas. With mixer on low, add half-and-half and beat until just mixed. Add chives or scallions and mix until just combined.
Dump dough on well-floured board and knead lightly into rectangle 3/4-inch thick. Cut out rounds with 2 1/2-inch round cutter and place on sheet pan lined with parchment paper. Brush with egg wash.
Bake for 20 to 22 minutes, until the tops are browned and insides are firm. Serve warm.