I tried this ratio and it worked, but you could cut the butter by half if you're trying to reduce your fat intake. You may need to add a little extra maple syrup or even a couple teaspoons of vanilla. Essentially you adjust the proportions of each ingredient until you have a soft, spreadable frosting.
1/2 cup butter, softened
2 cups icing sugar
1/4 cup maple syrup
1In a medium bowl, beat the butter with half the icing sugar until creamy. Add the remaining icing sugar and maple syrup and beat until well blended and smooth, adding a little extra sugar or syrup as needed to achieve a spreadable consistency. Makes enough for 2 dozen cupcakes.