Croquetas are the dish most tied to the group's identity. The cooking runs on a cult of fresh, seasonal produce, the kind long served in Madrid's markets, and the group's spirit is pure taberna: order a few tapas and end up toasting with champagne.

Grupo Arzábal is run by Iván Morales and Álvaro Castellanos. What began as a single tavern became, 15 years later, a small group, on a simple creed: eat better in a taberna than in any restaurant, order a few tapas and end up toasting with Champagne, and always ask whether another table could go here. The first Arzábal opened in May 2009 at Calle Doctor Castelo 2, a taberna with five tables and three staff, where the group's Japanese restaurant Kirikata now stands. Within months demand pushed them round the corner to this larger space where Doctor Castelo meets Menéndez Pelayo, facing the park, the old royal garden turned public park for all Madrileños, and it has been the group's mothership ever since. It holds one Sol in the Guía Repsol.

Arzábal is named after a clifftop meadow in Lekeitio, in Bizkaia, where local kids jump into the sea; mothers tell them not to go to Arzábal, and some jump anyway. For Castellanos and Morales, opening a restaurant meant the same thing: daring to take the leap. The two met in 2008, both graduates of Madrid's Casa de Campo hospitality school; Castellanos had worked front of house as a maître, and Morales in hotel management. They got on through a food club of friends who tried a Madrid restaurant on the first Monday of each month, and soon they were signing papers at the notary.

They didn't like the tabernas Madrid had at the time and wanted something different and fun: a DJ, half portions and a long list of wines by the glass, which were small revolutions then. At the end of 2018 the Retiro taberna was fully refurbished and took over the premises next door, doubling its space to about 200 square metres split between the bar and the dining room, with a terrace looking onto the Retiro. After that refurbishment the carta ran past 70 dishes, before off-menu seasonal specials, and the wine list to more than 650 references, about 125 of them by the glass.

The cooking is cocina de la memoria, memory-based cooking, built on a cult of fresh, seasonal produce, and many dishes come as a half or full ración. At the bar there's pan de cristal with tomato and olive oil (€6.50), dressed burrata, Negrini mortadella, premium León beef cecina, acorn-fed Ibérico ham, Sorlut oysters and a gilda of red tuna and anchovy. To share, there are Ibérico croquettes made with Latxa sheep's milk, a Russian salad with bonito belly, a bikini of cecina and Comté, garlic prawns and crispy pig's ear with brava. Spoon dishes include verdinas with baby squid (€22), a small casserole of callos (€14 or €19), patatas a la importancia with langoustines (€14 or €27) and arroz del senyoret (€24). Fish runs from a bonito tartare with ajo blanco (€23) to grilled monkfish for two (€59), and the meats from a grilled beef burger (€24) and suckling lamb chops (€32) to a steak tartare of beef tenderloin (€29) and a 45-day-aged Rubia Gallega chop at €115 a kilo.

Beyond Retiro, Arzábal runs El Jardín de Arzábal, a restaurant inside the garden of the Museo Reina Sofía, a restaurant at the Santiago Bernabéu stadium, and a counter at the Mercado de San Miguel. The group sums up its idea as reserving the best seats in Madrid: a bench in the Retiro, a chair in front of Guernica, a bar in San Miguel, a seat at the Bernabéu. The group took the taberna into the Museo Reina Sofía in 2016 and became the main bar operator at the Mercado de San Miguel in 2018; by its tenth anniversary in 2019 it employed more than 200 people. The founders say they wouldn't open a restaurant they wouldn't go to as customers.

Arzábal Retiro is at Avenida de Menéndez Pelayo 13 and opens every day from 12:30, until 01:00 early in the week, 02:00 at weekends and midnight on Sunday. Book online through arzabal.com, call +34 914 095 661 or email info@arzabal.com. Tables go fast, so booking ahead is recommended. Gift vouchers are sold on the site.