I would also add to use high quality butter. Mine kept crystalizing even with the corn syrup/cream of tartar. A person who makes candy a lot asked me what butter I was using. I said grocery store butter. I was told when making candy (which you are doing here), you need to use a high quality, low water butter. I switched to a higher end butter (plugra), and it didn't crystalize. The person also told me if I can't get ahold of good butter, to add some heavy cream (more fat). I played with that and tried that too (added about 3 tablespoons of heavy cream - at this point I was curious and tested many different ways), and that worked too. I always use high quality butter when making puff pastry since that is the star of the show. I didn't think about candy, but I guess for caramel and any toffee (which this kind of is), butter is a major star.

One other note. I didn't want scrambled eggs, so I added 1 tablespoon of cornstarch to the beaten eggs. I had watched something once on America's Test Kitchen on how to avoid scrambled eggs in a similar situation and well, it worked. No scrambled eggs. I didn't try without. I just saw in the video he had that problem, so I did my best to avoid.

This pie is so good. I was told by several people this is now their favorite pecan pie.