Sardinia — the myrtle (mirto) is the most characteristic plant of the Sardinian macchia, and its use in cooking, liqueur production, and post-roasting flavoring is unique to Sardinian culture. The myrtle-rest technique is specific to porceddu and to some lamb preparations in Sardinia.
While porcetto allo spiedo (spit-roasted suckling pig) is the most famous Sardinian meat preparation, porceddu al mirto is its complement: the roasted suckling pig rested under a blanket of fresh myrtle branches for 20-30 minutes after cooking. The myrtle (Myrtus communis) grows wild throughout Sardinia and its volatile aromatic compounds (eucalyptol, limonene, α-pinene) transfer to the hot pig skin during resting, infusing the meat with a complex herbal, citrus-pine fragrance that is unmistakably Sardinian. The myrtle rest is what distinguishes Sardinian roast pork from all others.
Porceddu al mirto has a specific, complex aroma that no other preparation replicates — the crisp, golden skin carries a pine-citrus-herbal perfume from the myrtle that is distinctly Sardinian. The flavour of the meat itself (the suckling pig's sweetness from the milk diet) is accented rather than dominated by the myrtle. It is the flavour of the Sardinian island — its macchia, its light, its particular air.
The myrtle-rest technique: after the suckling pig has been roasted on the spit until fully cooked and the skin is copper-crisp, remove from the heat and immediately cover the entire pig generously with fresh myrtle branches (not dried — the volatile aromatics of fresh myrtle are essential). Cover the myrtle with a cloth or second layer of branches to trap the perfume. Rest 20-30 minutes — the steam from the meat carries the aromatic compounds from the myrtle into the skin and exterior meat. Remove the myrtle and serve immediately. The skin should be golden, crisp, and fragrant with the unmistakeable pine-citrus aroma of myrtle.
Fresh myrtle must be gathered on the day — the aromatic oil content decreases rapidly after cutting. In Sardinia, myrtle grows abundantly in the macchia (Mediterranean scrubland) and is gathered freely. Outside Sardinia, fresh myrtle is occasionally available at Italian specialty food shops or from Mediterranean plant nurseries. The myrtle berry liqueur (mirto rosso or mirto bianco) is the digestivo served after the meal.
Using dried myrtle — it has far less volatile aromatic compound content; fresh myrtle must be used. Resting too long under the myrtle — beyond 40 minutes, the skin softens and the myrtle aroma becomes overpowering. Not covering with a cloth — without insulation, the steam dissipates and the myrtle aroma doesn't transfer effectively.
Giorgio Locatelli, Made in Italy; Slow Food Editore, Sardegna in Cucina