While the cupcakes bake or cool, make the frosting. Let vegan butter soften but not melt in a mixing bowl. Beat until creamy, about 30 seconds. Add powdered sugar, aquafaba, vanilla, and salt. Beat on low to combine, then beat on medium high until smooth, about two minutes. If butter starts to melt, pop the bowl in the fridge for 10 minutes or so, then continue. When frosting is creamy and smooth, cut basil into ribbons, and immediately use a spoon to stir basil into frosting. (If you wait, the edges will turn brown.) Optionally, add food coloring “to taste.” If you will be piping the frosting, spoon it into a pastry bag. Refrigerate until needed.