Cream the butter and sugar together with an electric mixer until fluffy. In a separate bowl, combine the flour and salt. Mix the flour into the butter mixture, alternating with the sherry, making sure to finish with the flour. Stir in the ground pecans.
Drop by the teaspoonful onto a cookie sheet and roll each portion between your palms to make smooth, even balls. Press each one into the cookie sheet and brush with beaten egg white. Using a fork, knife or another tool, press a design into the top of each cookie, or press a pecan half, right side up, into each ball or dough. Bake in the preheated oven for 25 minutes. Remove from the oven, let cool a few minutes and remove to a wire rack to cool completely.
Cool and let cookies sit overnight to ripen. Serve or store in an airtight container for up to 1 week.