Using a knife, cut the margarine into small pieces and place in a 1-quart bowl. Add the flour, and use your fingertips to work the ingredients into a smooth dough.

Transfer the dough to a lightly floured board, and knead for 2 minutes, or until the mixture is shiny and pliable.

Coat a sheet of plastic wrap with nonstick cooking spray. Shape the dough into a ball, place in the center of the plastic wrap, and wrap tightly. Store in the refrigerator for up to 10 days.

To use the Beurre Manié, add 1 tbsp of the mixture for each cup of sauce, soup, or stew liquid. Bring the liquid to a boil over medium-high heat. Remove the pan from the heat, add the Beurre Manié, and quickly blend with a whisk until the mixture is smooth. Return the pan to the heat and bring the liquid back to a boil, at which point it will thicken instantly.