In a basement cooking school in San Sebastián's cobblestoned Old Town, it was simple and comforting: soak yesterday's bread in milk infused with cinnamon, sugar, and vanilla, then sauté it, and serve it for dessert. Homey slices, golden-crusted from the egg and flour, each bite yielding a warm milky fluff of cinnamon and lemon.

As we sampled our creation, I was busy writing in my grease-stained notebook "custardy, barely sweet...yum." Judy Kravitz, a friend from New Jersey, was snapping photos of the final dish, known here as torrijas.

Coming as it did after the thoroughly delicious red piquillo peppers stuffed with cod that we had just made, it was the perfect ending to an afternoon filled with culinary excitement and invention. And it was just the beginning.

We were eight women of middling years on a weeklong gastronomic sweep through Spain's Basque country. As restaurant critic for The Washington Post for 23 years, I had visited France, Italy, and the Far East. But lately, everyone had been talking about Spain—and San Sebastián, in particular—as the new world center of creative cooking. The last time I was in Spain was in 2000, to spend two days at the futuristic restaurant El Bulli—sampling savory ice creams, warm gelatins, and deconstructed soups. Now even American chefs were talking about "molecular gastronomy," a new approach to cooking that involves rethinking everything from temperature to texture to taste.