What it communicates: You hate her cooking and/or are a mysoginist.
Tread carefully with this one. If you buy the class just for her, you're walking on shaky ground. If she's not passionate about whipping up souffles and making a proper Hollandaise, she may wonder if you're insinuating something about her cooking. Even worse, she might take it as a misogynistic gesture that implies she should be permanently barefoot and in the kitchen.
The best way to avoid this is to purchase a class you can take together. The implied meaning will be that you're eager to spend time with her outside of a bar and/or bedroom, and that you're interested in learning to cook for her. Which is great, because whipping up Annie's Mac and Cheese is not the formula for romance.