Sardinia — porcetto sardo is ancient; it appears in Nuragic-period sources and was described by ancient Greek and Roman travellers to the island. The myrtle resting technique is specifically Sardinian and may relate to the island's abundance of wild myrtle (Myrtus communis), which grows throughout the island's macchia.
Porcetto sardo (or porceddu, the Sardinian term) is the feast preparation of Sardinia — a whole suckling pig (3-5kg) or young pig (8-10kg, the more common version for the 'maialetto') cooked slowly for 4-6 hours on a spit over live oak and myrtle-branch embers, then in the final 30 minutes rested on a bed of fresh myrtle branches which, with the residual heat, perfume the skin. The myrtle resting is the Sardinian fingerprint — no other Italian spit-roasted pig uses myrtle in this way. The skin becomes lacquer-bronze and shatters when bitten; the meat is juicy, fragrant from the myrtle smoke, and has the clean sweetness of milk-fed pig. Served in the forest clearings at the traditional Sardinian 'sagra' festivals.
Porcetto sardo served on the myrtle branches is one of the most visually and aromatically striking presentations in Italian cooking — the bronze skin, scattered with myrtle sprigs, smells of wood smoke and fresh resinous herbs simultaneously. The first bite of skin shatters and is greaseless, crackling, and fragrant. The meat beneath is juicy, milky-sweet, and has absorbed the myrtle perfume through the skin. It is the preparation that justified the pilgrimage to Sardinia.
Season the whole pig inside and out with coarse salt only — porcetto needs no other seasoning; the myrtle provides the flavouring. Mount on the spit; secure the legs. Spit over live oak embers (never flame — the pig must cook from radiant heat, slowly rotating). The embers should be at the correct temperature: hand held 30cm away can stay for a count of 3-4. Maintain embers continuously for 4-6 hours; the pig rotates continuously. Internal temperature of thigh should reach 75°C. In the last 20 minutes, remove from spit; place on a thick bed of fresh myrtle branches; cover with more myrtle. Rest 30 minutes — the myrtle perfumes the skin with its resinous essential oils.
The correct wood is Sardinian oak (leccio, holm oak) — it produces a long-lasting, even heat without excessive smoke. Myrtle (mirto selvatico) branches are the finishing element — the volatile oils in the fresh myrtle branches release under the residual heat of the pig and perfume the skin. Without myrtle, the preparation is simply spit-roasted pig; with myrtle, it is porcetto sardo. Mirto liqueur (the Sardinian after-dinner digestif) is made from the same myrtle berries and leaves.
Temperature too high — the skin chars before the interior is cooked; maintain a consistent moderate heat from white-ash embers. Not resting on myrtle — the myrtle resting is not optional; it is what makes the dish Sardinian. Insufficient salt — the salt on the skin is the only seasoning; be generous.
Waverly Root, The Food of Italy; Slow Food Editore, Sardinia in Cucina