In a medium saucepan, melt the margarine over low heat. Add in the pecans and sauté for 3–5 minutes, until they begin to release a nutty aroma and turn a deeper brown color. There will seem to be a lot of margarine, but don’t worry, as you’re not looking for it to be absorbed or completely used up in this stage. Take out two separate bowls and drain the excess margarine into one, and move the toasted pecans into the other. Draining the nuts thoroughly is critical so that they don’t become soggy or greasy later on. Set the nuts aside.
Set a medium pot over the stove on medium heat and combine the leftover margarine, soymilk, soy creamer, sugar, salt, and cornstarch. Stir everything together until dissolved, and let the pot cook for a few minutes until the contents come to a steady boil. If the liquid threatens to bubble over, reduce the heat and whisk vigorously while heating for an additional 1–2 minutes, until the mixture feels slightly thicker. Remove from heat and stir in the vanilla. Let cool to room temperature before covering and moving it into your refrigerator to chill for at least 20 minutes.
Once thoroughly chilled, transfer the ice cream base into your ice cream maker and freeze according to the manufacturer’s instructions. During the final 5 minutes of churning, add in the pecans.