In order to fill frost and decorate the cake we made two batches, one with the basil butter and one with standard butter. The reason for this is because when you infuse the butter it can slightly change the consistancy, making the butter a little more grainy. We needed a smooth buttercream to create the stripes so we just used the basil butter cream in the filling and for a thicker crumb coat. A way to get the basil buttercream to be a little smoother is to make a Swiss meringue buttercream over an American buttercream.