Hellmann's Burguer-lovers Route

From past June 2nd to July 6th, Hellmann's is sponsoring a new idea in Madrid and Barcelona: a route of 20 restaurants in each city, that have created a new burger specialty that includes some Hellmann's sauce in the recipe. There are very original creations, from one that includes grilled peach, to other made of bison meat.
Users are invited to vote the best of them in the web, and a motorcycle will be raffled among the participants.
The restaurants in Madrid are scattered in the following districts: Centro, Retiro, Salamanca, Arganzuela, Chamberí, Moncloa-Aravaca and Chamartín.
There are traditional restaurants as the well known Alfredo's and the "Pecado Carnal" ("Carnal Sin"), and some newer ones, as The Mad Cafe.   Here's the list of all 20 participating restaurants in Madrid:

What are "Entresijos" and "Gallinejas"?

We've recently had in Madrid the festivities in honor of its patron saint "San Isidro" (which official day is May 15th). They're celebrated in the "pradera de San Isidro" (medow), where you can find many food stalls and fairground rides. Two of the most traditional foods in Madrid are "Entresijos" and "Gallinejas", and they can be found almost in every stall there these days.
But what are they? Find it below!