About 2 days before making your ice cream, steep your anise seeds in the soy creamer. In a medium saucepan over medium heat, combine the two ingredients together. As soon as it starts to simmer (do not let it boil), remove it from the heat and cover for at least 20 minutes. Pour into a jar, let cool, and place in the refrigerator for at least 24-48 hours.
About 1 day before making your ice cream, make the rhubarb sauce. Combine rhubarb, sugar, agave, water and vanilla in a large saucepan. Bring to a boil, stirring until the sugar is completely dissolved. Lower the heat and simmer for approximately 20 minutes until the rhubarb breaks down. Remove the pan from the heat and cool completely. Place in the refrigerator until ready to make ice cream.
Also be sure the bowl of your ice cream maker has been in the freezer for at least 12 hours before making the ice cream.
Place all ice cream ingredients in a blender and combine until thoroughly mixed. Add mixture to ice cream maker and follow the manufacturer's instructions. It should take about 15 minutes to thicken.
Once thickened, place about half the ice cream in a loaf pan or freezer-safe container. Top with half the rhubarb sauce. Top with remaining ice cream the remaining rhubarb sauce. Using a skewer swirl the ice cream and sauce together.
Cover with plastic wrap and foil tightly, and freeze for at least a couple hours. Once ready to serve, remove from freezer 30 minutes prior.