I have had only one experience at Essencia, in October 2014. I decided to try it on a visit to Porto based on various online comments. I was not disappointed. From start to finish, the quality of the food was very good. We both started with the pumpkin soup which was light in texture and subtly but deliciously flavored. I had the black-eyed pea dish which was very satisfying though the rice was a bit perfunctory. My wife had a risotto which was also very good. Our accompanying wine, chosen after sampling a couple of selections, was likewise delicious. Dessert was also of a high level, my wife's "Essence of Chocolate" was one of the best deserts we have ever tasted in a restaurant. I did not find the pricing to be unfair, as another reviewer has suggested.
My only complaints are that the staff was a little cool by Portuguese standards and one of our servers apparently had a cold and proceeded to blow her nose and sneeze without washing her hands in between our courses! Also, given the excellent bean cuisine of Portugal, some feijao Catarino and/or Encarnado-based dishes should be available.
In summary, Essencia is a a very good restaurant which I can strongly recommend and I will return on my next visit to Porto.
Cons: Staff a bit aloof, Needs more bean-based entrees