Yelp, and pure happenstance. Here are the ones with photographic evidence.
Moz Heart in the Mercado de San Miguel. They have numerous rolls and toasts featuring mozzarella and burrata. Rolls were 1/8" thick mozzarella wrapped around various ingredients like salty cured meats. The toasts were topped with creamy burrata topped with olive oil and some black pepper. I bought the salmon topped burrata and the jamon/mozzarella/arugula roll for €3.50 each. They seemed expensive to a friend, but such quality mozzarella and burrata is hard to get in Colorado (exceptions at Osteria Marco and the Denver Truffle).
I discovered Alboraya when looking for another ice cream place. They had just opened that morning and I walked in to peer at their selections. Horchata! Sold. And then Turron. Ice cream selected for 2.70. The Horchata featured chufa's distinct flavor quite well. The Turron had the ground almond taste that I'm accustomed to. I was pleased with both flavors, the density, and their lasting impression on my palate. Superb flavors local to Spain! To my poor Denverites drinking Mexican Horchata or eating Sweet Action's mexican horchata flavored ice cream, there's no comparison. Chufa trumps all.
Le Cabrera. I literally ran out the door once I read the reviews. As I perused the menu while snacking on complimentary herb and paprika dusted chips, I came upon the Claymore, a cocktail featuring Pisco, Islay Scotch, Green Chartreuse, and creole bitters. Herbal frothiness topped my chilled silver glass. Apparently, it did contain egg white. Once I got through the foam, I was greeted with the earthy bitterness and smokiness from the Scotch. Delicious.
DF Bar Tortería Mexicana was another pleasant surprise. I was en route from Anton Martin to Puerta del Sol after a private lesson. I was hungry and on the prowl for something cheap and not kebab. This place was packed with locals and I remembered tortas as being a delicious messy Mexican sandwich. Ever read Denver on a Spit? You should.
I selected what sounded the most authentic to this non-Spanish speaker, the Cuauhtemoc features nopal y huevo. I never had cactus until visiting Madrid and the taste was growing on me. Thanks, Taqueria mi Ciudad. As I waited, they started me with jalapeno and cilantro chips. Crunching away, I watched my sandwich being grilled beans, avocado, tomato, and cheese filling the remainder. Delicious. I wish I could have gone back there. Interesting note: Several of the Taqueria mi Ciudad guys wear DF shirts.
Fat Boy Burrito was my best find. Yep, I discovered a brand new restaurant in Madrid! I found Fat Boy when wondering between Chueca and Tribunal seeking vintage shops. I took a photo of their outside and hunted for information online. I finally found information via their Facebook and discovered they opened two days before I visited.
I chose the moderno burrito with the ignacios (chips with guacamole). I first tasted apple when tasting this burrito. I'm not sure why since I expected mango or some habanero. Eventually, I got into the delicious pollo pibil with its orange char and earthy taste, onyx black beans, and padron fritos. The chips were great also especially paired with the foamy guacamole.
Other notes: the staff wear cool buffalo plaid shirts, have such precision when piecing the burrito together, great interior colors, friendly service (+ English), great chilled out music with stellar beats. Go here.
That wraps up Madrid. There were a few other restaurants I discovered, but I didn't have my camera with me. My Madrid food advice: find a Madrid foodie whether it's a friend or a local's blog. There are many restaurants that serve typical Spanish cuisine, but much of this is underwhelming. This is why you need someone passionate about food.