Tortellini

A tortellino starts as a three-centimetre square of egg pasta with a hazelnut of filling in the middle. You fold it into a triangle, press the edges, turn the base up and wrap the whole thing around the tip of your index finger until the two points meet. The result is a small ring with a raised crest, and if there is no ring, it is not a tortellino.

Size is not a detail. A properly made tortellino weighs three or four grams, which means 250 to 350 of them in a kilo. The walnut-sized things sold in most supermarket chill cabinets are a different product; in Bologna they have a blunt name for them.

The filling is meat and cheese. Since 1974 the recipe has been lodged with Bologna's Chamber of Commerce by the Dotta Confraternita del Tortellino and the Italian Academy of Cuisine, and that document remains the reference point for the city: pork loin browned in butter, prosciutto crudo, mortadella di Bologna, Parmigiano Reggiano, eggs and nutmeg.

The first thing you taste is Parmigiano, which surprises people who expect meat. Parmigiano is the largest single ingredient in the registered filling (450 grams against 300 each of the three meats) so the flavour is nutty, salty and savoury before it is porky.

Then the cured meats arrive: the sweet-spiced note of mortadella, the deeper saltiness of prosciutto, the roasted richness of the pork loin. Nutmeg runs underneath everything, warm and just short of assertive.

In broth the texture matters as much as the flavour. Hand-rolled pasta is porous and slightly rough, so it holds the broth rather than sliding through it, and each tortellino delivers a small burst of hot filling into a clean, golden, faintly sweet capon stock. That combination of rich parcel and clear broth is the whole point, and it is why Bologna resists the cream sauces the dish acquired abroad.

Cook them in broth, not water, and serve them in the same broth. That is the traditional method and the reason the dish exists. A good capon or chicken-and-beef stock, started from cold water with celery, carrot and onion, skimmed carefully and strained clear, takes three hours and is half the recipe.

Drop the tortellini into simmering broth (never a rolling boil, which tears them) and give them two to three minutes if fresh, four if frozen. Serve immediately in warmed bowls, with grated Parmigiano offered separately for those who want it.

Count forty to fifty pieces per person for a first course, about 150 grams of hand-made tortellini. If you are working with larger packaged ones, 100 grams is plenty.

The alternatives Emilians accept are few: tortellini asciutti, drained and tossed in melted butter with Parmigiano, and deep-fried tortellini as a party snack. Cream sauce is a 1970s export and is not served in Bologna. Ragù on tortellini is considered a waste of both.

There are two situations and they behave differently. A vacuum pack carries a date, the maker's reference, and stays sealed at 2 to 4 C until you open it. Once open, the sheet begins losing water to the air within hours and the pieces stick to each other wherever they touch. Loose fresh tortellini go in the fridge on a floured tray under a cloth, spaced in a single layer, for about two days. Do not shut fresh ones in an airtight box: trapped moisture glues them together and the filling wets the pasta from the inside.

Freezing is what every household in Emilia does in December. Spread them apart on a tray until hard, then bag them: three months at minus 18 C, dropped into the broth still frozen and cooked in roughly four minutes. Thawing first is the mistake, because they slump and stick. Left long in the freezer the exposed pasta dries, the edges go pale and brittle and the filling darkens. Broth keeps three days in the fridge and freezes for months; skim it cold, once the fat has set into a solid layer.

Size settles it before anything else. A Bologna tortellino weighs two to five grams and vanishes in a spoon; anything heavier is a cappelletto under another name or an industrial shape. The seal should be crisp, the two points properly joined and the central fold standing up, with no filling showing through. The sheet is matt and slightly rough, never glossy or rubbery: shine means a machine sheet and a dough carrying too much water. Cooked, the filling reads as Parmigiano first and meat second, with nutmeg present but not leading.

Abroad the same word covers three different things. Dried boxed tortellini from the pasta aisle are a cheese or ricotta shape with nothing of Bologna in them; the chilled deli packs are closer; tortelloni are two or three times the size and usually ricotta and spinach. Read the filling list on any pack: if breadcrumb or chicken comes first you are a long way from Emilia, and cooked ham in place of prosciutto crudo marks the budget version. Fresh from an Italian deli costs several times the boxed price for the same weight.

In the US, fresh tortellini from Italian pasta shops and delis run 14 to 24 dollars per pound and are worth seeking out over the chilled supermarket versions; Eataly, Di Palo's in New York, and regional Italian markets in Philadelphia, Chicago and Boston all make or import them. Frozen imported tortellini from Emilian producers are stocked by Italian specialists online.

In the UK, Italian delicatessens and online importers such as Vorrei and Natoora carry fresh and frozen versions; supermarket own-brand fresh tortellini sit around £8 to £14 per kilo and are a different category of food.

What to check: the ingredient list. If the filling starts with breadcrumb, chicken or pork trimmings rather than named cured meats and Parmigiano Reggiano, expect a bland result. Size matters too: smaller is better, and anything over about eight grams a piece will not behave properly in broth. If you buy dried tortellini, treat them as a store-cupboard convenience rather than an approximation of the fresh original.

Bologna is the obvious place, and tortellini in brodo is on trattoria menus year-round. The pasta shops of the Quadrilatero, the old market streets behind Piazza Maggiore, have sfogline rolling pasta by hand in the window: worth ten minutes of watching before you eat.

Modena claims the dish just as loudly, and the border town of Castelfranco Emilia, where the Venus legend is set, holds a tortellino festival every September. The Modenese filling leans a little more on mortadella.

Up in the Bolognese Apennines (Vergato, Loiano, Monghidoro) mountain trattorias serve richer broths and bigger portions at lower prices. And in Parma, an hour up the Via Emilia, the equivalent dish is anolini in broth: eating both in the same week is the fastest way to understand how specific Emilian pasta traditions are.

December is when the city takes it most seriously, since tortellini in brodo is the Emilian Christmas dish and families roll their own on the 24th.