Few dishes are as versatile as the potato omelet served in Spain. Consisting of little but eggs, potato, onion, and olive oil, it is a recipe passed down in the genes of Spanish cooks. That every one tastes different is a mystery.

This morning, as we set out researching the Barcelona chapter for Frommer’s Easy Guide to Madrid and Barcelona, we decided to have breakfast the La Boqueria – technically Mercat Sant Josep, but only called that by city bureaucrats. It is the jewel of Barcelona’s three dozen local food markets.

All the way in the back, where the market comes out on Carrer Jerusalem, is La Gardunya (C/ Jerusalem, 18, tel: 93-302-43-23), one of the oldest and most venerable of the market restaurants. Contrary to what most people think, it’s open for breakfast as well as the more famous lunch and dinner operation. We sat in the “garden” where we could watch the vendors delivering all manner of fresh food to the stalls, and ate classic tortillas españolas made fresh and served with a side of pa amb tomaquet – slices of baguette rubbed with raw tomato, sprinkled with salt, and drizzled with olive oil. It’s a classic Catalan dish. The bread was part of the tortilla service – less than 4 euros.

At the end of the day, we discovered a brand new restaurant at the Hotel Adagio in Barcelona’s Gothic Quarter: Adagiotapas (C/ Ferran, 21, tel: 93-318-90-61). It’s a pretty daring venture for the modest hotel, as the menu is from Jordi Herrera, a chef whose other restaurant in Barcelona’s L’Eixample district near Sagrada Familia, Manairo, was awarded a Michelin star this year.

We happened to run into Herrera at Adagiotapas, and he couldn’t have been nicer. The concept is simple. He reinterprets some of the great tapas of Spain with his own creative twists. For example, instead of ham croquettes, he serves delicious rabbit croquettes encrusted with shredded phyllo and accompanied by a few dabs of ratatouille.

As for the tortilla española – which is usually served as a small slice for a tapa – Herrera makes a super intense tortilla. (We think he may use a little pork fat along with the olive oil and he certainly caramelizes the onion). He then finishes it in the oven as a small tart cooked in a cupcake paper. It is the perfect foil for either a glass of white wine from Rueda, or a Campo de Borja rosé. We couldn’t help but smile when our server brought us a plate of pa amb tomaquet.

Same ingredients – perfect at either end of the day.