Overwintering Chocolate Cosmos

I purchased two chocolate cosmos this summer to use in planters. They were about $6 a piece. I loved the chocolate-scented, red velvet blooms on long stems amid airy foliage. But in our climate, I don't think they would have survived the winter. So, I chopped off all the foliage and re-potted them to bring them inside. At first, I assumed I had killed them, but new stems are growing. Below is a picture of one of the flowers from this summer. 

Chocolate Cosmos

My mom told me I HAD to grow these this year. I assumed it would be no big deal. I'd just get a packet of seeds, since cosmos are easy to grow. Wrong. These cosmos aren't available as seed. The plants are sterile and only available through propagation. I did locate two plants. They do smell just like chocolate.