Put the margarine and pecans in a saucepan or heavy skillet. Bring it to a low simmer and let it simmer for about 15 or more minutes. Toward the end, you'll want to watch it carefully as the butter (and pecans) will burn if you leave them too long. Mine is usually done around 18 minutes or so. If you are nervous, it's better to take it off the heat early than late. It will still taste good. Strain out the pecans and let cool.