It costs close to $200/month for three clicks a day in the baking categories in my area. For example, once three random people click, you disappear.
If there are only a few lessons offered in the area, you could design a website (required for the above also) with the right key words. But in both cases, people will have to be looking for the lessons.
You may want to make a brochure and visit places where you may have potential clients. It may make a nice bachelorette party or shower event. Civic leagues and womens clubs are another source. But be sure not to violate any "no soliciting" notices. In most cases, to get to these people you will have to pay to be in a newsletter.
There really is no free advertising. Even sampling can be quite costly if you use fine ingredients.
Most of the time I have seen lessons work is when an established business that people really love starts offering them. It is incredibly difficult to break into this industry without a strong following.
For example, I'm paying for an advanced painting class in November. It will make me money and the decorator is well established and respected. It is quite expensive. I wouldn't be paying for this if I didn't know the artist's work.
Another thing you can do... still not cheap... is to do your demonstrations for charity or at better local craft events and fairs. You could demonstrate and give samples of the food as you were making it.
You may also be able to rent a booth, or area, in a retail store for the same purposes. Tasting your food at an event, offering a discount for signing up and paying right then, and a great, professional setup will make them want to do what you do.
It all costs and it requires startup energy, but what good plan doesn't? It is totally doable if your level of commitment is there. And give it time. There is a recession and this is purely a luxury item, but people buy luxury items every day.
Good luck with your venture and make sure your site and business cards are in place before you start.