It is pretty straightforward.
It is worth understanding the source of bitterness of pecans. They have two sources, naturally occurring tannins in the kernel and pieces of corky material from the inside of the nut shell which can adhere to the kernel. Some of the tannin and all of the corky material can be removed by washing the kernels before cooking.
To "sweeten" the pecan meats, simply put them pecan in a bowl and fill with lukewarm water. Stir and tumble the meats in the water for several minutes and you will see the discoloration in the water. Pour off that water and repeat the process at least once more. You will notice that the water becomes less and less discolored. Spread the pecans on a paper towel and allow them to dry for 10 or 15 minutes. Drying is not necessary if the pecan kernels are going to be oven roasted. To roast the pecan kernels, spread the kernels evenly in a pan with sides (to allow stirring without spillage) and put in a pre-heated oven at 350 degrees F. Cook for 10 minutes, stirring every couple of minutes. Alternatively, allow the pecans to dry them toast in a dry pan.
Extracts are made with alcohol. Some use rum or brandy for nut extracts, especially for pecans and hazelnuts, but I prefer high proof vodka or grain alcohol. (I usually use the former.) I do not care for extracts that taste of other flavors. Use a dark glass bottle. The ratio of nuts to liquid as well as the size of the nut pieces (plus the steeping time) determines the outcome. I like 3/4 cup finely chopped nuts per cup of alcohol. Stir well. pour into the bottle, then steep for two months. Strain. Done.
