Combine egg whites (at room temperature) and 1/2 cup sugar in a medium mixing bowl; beat until mixture is foamy. Add ground almonds, flour, butter, and flavorings, stirring until well blended.
Drop by heaping teaspoonfuls 2 inches apart onto three well-greased cookie sheets. Use a fork dipped in water to flatten cookies.
Bake one sheet of cookies at a time at 350° for 8 minutes or just until lightly browned around the edges. Cool 30 seconds on cookie sheet; immediately loosen each cookie, and bend each around a rolling pin. Press gently against the pin for a few seconds. Slide molded wafers off pin, and place on wire racks to cool completely. Repeat baking and shaping procedure with cookies on remaining cookie sheets. Store cookies in an airtight container.