Bring water and molasses to a boil in a saucepan. Meanwhile, melt the butter in a separate saucepan over low heat. Stir in the flour and cook, stirring occasionally, for a few minutes until the dough begins to pull away from the sides of the pan.
Pour the molasses mixture into the flour, stirring to form a ball. Fold in chopped walnuts. Drop onto waxed paper by the spoonful, and allow to cool completely before serving. Store in an airtight container.