Despite mixed reviews of this place online, we decided to give it a shot. Unfortunately, I agree with those describing it as mediocre.
Everything we ordered was very greasy and most of the dishes were bland. We ordered octopus and it was overcooked to a rubbery consistency. The bacon-wrapped pork medallions also did not impress, as the bacon was undercooked. We also ordered a dish described as "wild" mushrooms, only to find that they were just sauteed button mushrooms. In looking at the menu, the prices seemed reasonable, but the dishes were really tiny. I would not call six dollars for a few button mushrooms or seven dollars for four cocktail sausages a good value.
As far as being authentic, that may be true. The dishes offered were similar to what we found in tapas restaurants in Spain and did not try to be pretentious fusion concoctions. Truthfully, we found a lot of overpriced and mediocre food in Spain, as well, so maybe "authentic" is the best thing I can say about La Tasca.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.