In a large kettle (about 8 quarts), combine Isomalt, baking soda, buttermilk and salt or salt substitute. Cook over high heat 5 minutes, being sure to stir frequently and to scrape bottom and crevices of kettle. Cook to 234 degrees F. on a candy thermometer. Remove from heat. Add margarine and 2-1/3 cups pecan halves. Cook stirring continuously to soft ball stage. Remove and let stand just a minute or two. Then with a spoon, beat until thickened and creamy.
Immediately drop by 2" tablespoonfuls onto waxed paper or a cookie sheet. Dot with perfect pecans. Press pecan into each piece of candy.