“I beg your graces’ pardon.” The old woman was wringing her hands, tears starting from her eyes. “I have only fish and eggs to offer you.” It was 1969. My companions were priests — fellow residents of my student hostel in Salamanca, where they were studying to be canon lawyers. In their rickety little Seat we were on our way to see the heart and arm of St Teresa in Ávila.

In her front parlour our hostess kept a modest eatery in Peñaranda de Bracamonte, high on the Castilian plateau — a crumbling village of gold stone and stained stucco, now renowned for its roast piglets. It was a Friday in Lent: hence the restricted menu. Because Spaniards are exempt from Friday observance for the rest of the year, Lent is scrupulously respected.

The priests were in the tenue of the time: cassocks and beaver hats. The old lady can have had no doubt of their clerical status. Yet she hardly expected the clergy to conform. It was like stepping into a pre-Reformation past.

“Bless you, my child,” pronounced the elder priest as he waved the cook back into the kitchen. We sat down to sumptuous merluza en dos salsas: sear the hake before baking with plenty of garlic; make one sauce out of stock from flambéed shrimp shells with shrimps and finely chopped tomatoes, the other from asparagus purée. Garnish with prawns and quarters of boiled egg.

Gourmands have always bucked taboos: Charlemagne’s fast days featured whole salmon, sturgeon and fat eels. One Friday in the 1180s Gerald of Wales expressed surprise at feasting on barnacle goose with the canons of Canterbury, who justified their extravagance by explaining — disingenuously, I suppose — that the beast in question, “like fish,” did not reproduce sexually. By that criterion, I suppose, our seasonal dishes should be of plankton or amoebas.

Abundance and consumerism now clog Lent with glut. Demonisation of meat and deification of fish have made piscatorial menus laughable forms of penance. You might appease conscience while feeding greed with a menu after the heart of Salvo Montalbano, the self-indulgent Sicilian detective in Andrea Camilleri’s novels: fishy antipasti (smoked salmon, maybe, mussels in vinaigrette, mousseline of salt cod, octopus carpaccio), followed by spaghetti alle vongole (the inspector regards parmesan as an heretical addition) and triglie al sugo (if British fishmongers cannot supply suitably small mullet, fresh sardines will serve).

Gourmands have always bucked taboos: Charlemagne’s fast days featured whole salmon, sturgeon and fat eels.

But such a meal hardly seems luxurious enough to defy calls to austerity. I suggest caviar, followed by lobster bisque, goujons of sole, a baked turbot topped with tangy beurre vert, and angels on horseback as a savoury; or a few oysters, vichyssoise garnished with shrimps, octopus á feira (boiled slices with olive oil and paprika) and lobster thermidor, closing with anchovy fingers (which are best accompanied with viscous Pedro Ximénez Oloroso or coal-black coffee, rather than the champagne I’d want to conclude the previous menu).

What if you really want a self-sacrificial Lent, to recall Christ’s privations in the desert, or to save money to give the poor? Locusts and wild honey have biblical authority, but are somewhat impractical. Rather, craft meals around potatoes — the only food which, if you eat enough of it, guarantees total nutrition on its own.

Sautéed until crisp with garlic and onions, and sprinkled with very coarse salt, potatoes are insuperable. In the Canary Islands, where I lived indigently in my youth inside a piece of corrugated tin on a rooftop amid the tiles and towers of La Laguna, I acquired a taste for papas churriadas: boil in heavily salted water until the potatoes are dry and crusted; serve with mojo picón (squash hot red peppers in a mortar with garlic, breadcrumbs, olive oil and wine vinegar) or mojo verde (same, but with parsley instead of peppers and only a little sherry vinegar).

A few beaten eggs can turn potatoes — thinly sliced and cooked very slowly in olive oil, with lots of garlic, until tender — into a Spanish omelette, one of the world’s cheapest treats.

I recall a nun’s recipe for patatas al ama cura — “potatoes fit for priestly love”. You breadcrumb and fry thick slices before immersing them for half an hour in a simmering sauce of well-sieved tomatoes, onions, garlic and parsley with a pinch of sugar.

Bound in béchamel, with onions and whole black peppercorns to enhance the flavour, and bits of carrot and asparagus for texture, taste and colour, potatoes (roughly cube and lightly boil them in advance) make a sublime pie under shortcrust pastry. Or there´s potato salad, which truffle mayonnaise greatly enhances.

But my thoughts and salivations are edging me back towards seasonally unsuitable over-indulgence. It may be better to abjure fasting and do penance with extra prayers or good works. Back to the lobster. Maybe, as a concession to piety, cut out the caviar?