Cover the bowl with a cloth or plastic wrap and allow to rise in a warm place until doubled in size (an hour or two depending on the ambient temperature). In the meanwhile, line two cookie sheets with parchment paper. When the dough has risen, scrape it out onto a lightly floured surface and break it into equal size pieces, a bit bigger than the size of a golf ball. Shape each piece into a ball and place them on the baking sheets. Cover with clean dishtowels or plastic wrap and let rise somewhere warm until puffy and soft, another 30-45 minutes . Preheat the oven to 350F. Before baking, whisk the egg and brush the tops of the buns with it. Bake one sheet at a time until deep golden brown on top, about 20 minutes.