Hello Karl, As you probably know, anybody can have a "forum"... So the key is an interesting and "unique" content here, therefore this is where you should put the most of your effort right now. You would need some active and creative members. You can try to find them by looking on other similar forums and approach them, maybe with some kind of "promo offers" like free coupons or just pay them if you can afford. Anyhow, good luck. Bart
Maybe you could search other "cooking forums" and write some posts + leave comments. Of course with a signature.
Start a cooking channel on youtube, maybe name it the same as your website name, or something close to it. Post videos kinda like what martha stewart does on her shows. Watermark each video with the website name. Then embed the videos into your forum. If you do not want to use youtube, then consider metacafe, break.com, dailymotion, yahoo video, my space or facebook. There are dozens of video hosting sites with new ones opening almost monthly. Take a look at my youtube channel, the link is in my signature. Its one thing to "tell" someone how to do something. Its another thing to show them how you did it. Youtube is 3rd top refer of traffic to my forum, with around 4,204 referrals a month.
What I generally like to do is find the 'cool' crowd of the forum, and pay them a few bucks to start stirring up your forum. Not only do you get enough members coming from all of the forums, but the clashing 'cool' crowds create enough conflict for interesting content for others. More and more join, and eventually, you've got a populated forum with a going conversation. Oh, and you drain the competitor forums of their active members