Preheat oven to 400°. In a large bowl, combine the flour, baking powder, sugar and salt. Cut in butter until mixture resembles coarse crumbs. Stir in cream just until moistened. Stir in chives and lemon zest. Turn onto a lightly floured surface; knead 8-10 times.
Pat or roll out to 3/4-in. thickness; cut with a floured 2-1/2-in. biscuit cutter.
Place 2 in. apart on a greased baking sheet. In a small bowl, whisk egg and water; brush over biscuits. Bake until golden brown, 15-20 minutes. Serve warm.