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