These bake thin and crisp; eat them with fruit sorbets and almost any flavor of ice cream.
Adjust rack to lower third of oven and preheat oven to 325 degrees F. Line baking sheets with baking parchment. Sift together the flour, salt, and baking soda. In a separate bowl, cream the butter with the brown sugar and add the egg, blending well. Stir in the flour mixture and the sesame seeds. Using a ½-teaspoon measure, drop batter by rounded spoonfuls about 2 inches apart onto the baking sheets. Bake for 6 to 8 minutes (cookies will puff at first, then flatten and brown). Set baking sheets onto a cooling rack. Cool cookies completely before removing.