When I first arrived in the city I wanted to learn how to make a great paella, so I did a course in the Boqueria market! it was awesome, you learn the basic dishes of Spanish cooking in a kitchen inside the actual market! The course is great, you learn a lot and meet some great people, plus they also have other courses like Thai, sushi or Mexican.
You will learn a lot about cooking, but also about food and traditional products from a local chef, who will recommend great restaurants. The best part is that you get to meet likeminded people that love gastronomy.
Ask to dissect the cuttlefish, a truly fascinating experience!