Prepare the crust. To make it easy on yourself, you can use refrigerated crusts, which are a distant but still good second. To make a great homemade crust, use Martha Stewart's awesome recipe .
Spray cooking spray in a pyrex measuring cup or microwave safe bowl. Microwave chocolate squares for 3 minutes or until they are melted. Watch the microwave carefully. Don't let it keep going after it melts.
Add butter to melted chocolate. It can melt by itself or you can microwave it another 15 seconds.
In separate large bowl, mix sugar, salt, and flour. Stir in eggs and Karo syrup. Add Chocolate/Butter Mixture. Add Vanilla and Pecans and mix together.
Pour into pie shell. Bake at 350 for 60-70 minutes, until it slightly browned on top and a knife comes out clean.