1) Take a heavy 3 quart sized saucepan and mix the soda, buttermilk and sugar in it.
2) Cook over medium heat by stirring continuously until the soft ball stage of 234° is reached.
3) Add the vanilla and butter beating it slightly until it thickens a little.
4) Add the pecans, stirring them in.
5) Take a 9 inch square pan and spread the mixture.
6) Allow the mixture to cool, cut it into even shaped squares measuring 1 ½ inch and serve.