1. Line a pan with wax paper. Melt margarine in a saucepan on a low heat, gradually adding sugar. When thoroughly combined, add molasses, light corn syrup, and vanilla, stirring constantly.
2. When above ingredients are mixed, begin to add milk gradually, continuing to stir the mixture. Bring mixture to a low boil on a medium heat for 20-25 minutes, continuously agitating the mixture. Do not under any circumstances leave the toffee alone; it can easily boil over and burn.
3. Add thickener, as needed. Pour mixture into prepared pan, and place into the refrigerator until firm enough to cut into small cubes. If overly sticky on the surface, brush lightly with corn starch.
Definitely not a healthy dessert, but quite buttery-tasting and rich. Texture will vary depending upon the consistency of your nondairy milk, whether or not you choose to use a thickener, and the amount of sugar you choose to use.