Chef Ida Rodriguez
Line a large cookie sheet with wax paper. Brush with butter.
In a heavy sauce pan, combine all ingredients except pecans and vanilla. Slit vanilla bean down center, lengthwise, opening it with the tip of the knife.
Carefully scrape seeds from the bean pod and set aside. Save Vanilla pod to flavor in the future granulated sugar.
Slowly bring to a boil, until the piloncillo dissolves. Continue cooking, stirring constantly, until the mixture reaches 238-240 degrees.
Test by dropping a small amount into a bowl of water and it should form a ball. Remove saucepan from heat, add pecans and vanilla. Continue stirring as the candy cools.
When the mixture becomes creamy and cloudy, spoon the mixture onto the wax paper; about 1/4 cup at the end will make 18 pralines. Work quickly, before the candy hardens in the pan. The pralines set as they cool.