Have ready a wooden spoon, candy thermometer, pastry brush and cup of hot water to brush down sugar crystals from the sides of the pan. Also have handy 2 tablespoons to use for dipping and dropping the candy.
Line 3 baking sheets with parchment paper or foil, butter generously and set near the stove on a counter or table. (Don't use wax paper; the candy will stick to it.)
Clear the range top of all pots and pans so that you have plenty of work space. Chop the pecans coarsely and set on the stove.
Combine in a heavy 3-quart saucepan the sugar, baking soda, buttermilk or yogurt, corn syrup, ginger, butter, rum or vanilla extract. Place the pan on medium-high heat and bring the syrup to a boil, stirring until the sugar is completely dissolved, for 6 to 8 minutes, if needed.
Then, cover the pan and boil the syrup without stirring for 3 minutes. Remove the cover. Dip the pastry brush into the water and brush down the sides of the pan. Attach the candy thermometer to the inside of the pot.
Cook the syrup without stirring until it reaches 225 degrees, frequently brushing down the pan with the damp brush, and swirling the pan.