Marshmallow-Free Vanilla Creme Filling: In a mixing bowl, blend 2½ cups powdered sugar, ½ cup non-hydrogenated shortening, 1 tablespoon plain or unsweetened dairy-free milk beverage, 1 teaspoon vanilla extract, and a pinch of salt until smooth. Start with the mixer on low until the powdered sugar is mostly incorporated to avoid a dust cloud. Blend in more milk beverage 1 tablespoon at a time, as needed to get a thick but soft icing that you can roll into balls.
Shortening Note: This recipe was created with traditional Crisco. Non-hydrogenated shortening, like Spectrum, should work well, but some natural brands might cause more spread. Substituting dairy-free butter alternative will also cause more spread.
High Altitude: We haven't tested this recipe at higher altitude. If baking above 2500 feet, particularly if in a dry climate, adjustments should be made. I would personally try cutting the leaveners (baking powder and soda) in half as a first trial.