In General: Slow down your day.
Dinner is late, kicking into gear around 21:00 (9:00 pm). Most restaurants seem to shut down around midnight.
Breakfast is also late: God forbid you want a coffee at 7:30 or 8:00. Coffee is not my style at all….Americano style (i.e. weak and thin) with hot milk. Churros (fried, extruded dough) seem to come in 2 sizes. The fat ones you dunk in coffee. The skinny ones go into a pot of molten chocolate. Tortilla (potato/cheese) ‘omelette’ will keep you going for hours.

Restaurants
Eating at a Market:

Mercado di San Miguel – Beautiful market packed with stalls for tapas. Good wine selections. The croquetta guy was a disappointment. Bit pricey but we loved it. $$$ Plaza de San Miguel, s/n, 28005 Madrid, Spagna
Mercado di San Ildefonso –It’s a food court if you like that sort of thing. Some ladies upstairs have bangin’ good sausages. You can walk right by it because it looks like just a small store front. Go upstairs for the full court press. Calle Fuencarral, 57, 28004 Madrid, Spagna
Bicycle Cafe: funky, wear your tattoos, bring your laptop sort of place. Organic/Portland vibe. Huge portions. Plaza de San Ildefonso, 9, 28004 Madrid, Spagna
Calle Cava Baja: The whole street is Tapas Bar Heaven

La Chata: tiny, funky with a bar on one side and the restaurant on the other. The padron peppers are perfect. A glass of vermut is 1,80…a steal. Well priced: $ – $$ Calle Cava Baja, 24, 28005 Madrid, Spagna

Restaurante Esteban: More formal/traditional setting and the food is delicious! Matrimonios is a mix of dark and white anchovies. It’s a ‘thing’ in Madrid. For good reason.
On the list, but we didn’t get there:

El Respiro: jam-packed-with-millennials tapas bar, full beards & tank tops recommended
El Brillante
Tastes to Try at Home

Black squid ink paella: your basic paella but made with squid ink and slices of squid. Served with garlic mayonnaise (aioli) on the side. The aioli was pure white and we had a dinner debate about whether or not it contained whole eggs. My take is that it is commercial mayonnaise with a whole lot of garlic. Works like a charm. Kitchen hack: puree a whole head of garlic at a time and store in olive oil. Use with abandon.
Crazy stuffed olives: let your imagination by your guide, but you need giant pitted olives.

Pan con tomat: Basically ground fresh tomatoes, shows up everywhere and at every meal. Summer kitchen hack: grind up a bunch of fresh tomatoes and keep in the fridge. Instant tomato anything.
Baby squid with baby fava beans: a stewy mess of divine goodness. Secret seems to be finding pre-natal squid & fava beans. Sadly, I haven’t had much luck on that front.