I've worked full time in a professional field for 15 years. About 5 years ago, almost by accident, I starting making a small additional income from freelance work in a totally unrelated field. This has grown over time to the point where it's effectively an additional 10% on top of my salary and I've had the opportunity to work with some big names in this area. However, these commissions remain occasional. I perhaps do four pieces of freelance work in a month, often for four different clients.
I feel that I now have enough professional experience in my freelance work to apply for full-time work in this area. However, I have no idea how I could go about framing my CV. The traditional format of "employer name - betweeen dates - list skills/achievements" just won't cut it. The work I've done, although high quality and for well-known companies, is far too fragmentary to list in that way. Plus, if I listed it alongside my full-time work it would double the size of my CV and I've always felt keeping it short and sharp was the best way to go.
To further complicate matters, although my full and freelance work are unrelated, a few of the skills are transferable. Not many, but there are occasions I'd need to refer back to my full time job. Even if only to demonstrate that I've held down a successful career in a demanding field for 15 years.
How can I best go about designing a CV for a job based on my fragmentary freelance work?