Ingredients

Equipment Needed

• •Large marble or stone mortar and pestle
• •Small saucepan for blanching
• •Clean kitchen towel for peeling walnuts

Instructions

1. 1

   Blanch and peel the walnuts

   Bring a small pot of water to boil. Add the walnuts and blanch for 2 minutes. Drain and, while still warm, rub the walnuts in a clean kitchen towel to remove as much of the papery brown skin as possible. This step is tedious. It is also essential. The skins contain tannins that turn the sauce bitter and give it a muddy color. You will not remove every bit of skin. Remove what you can.

   Work while the walnuts are warm. The skins slip off easily when hot, stubbornly when cool. If they cool before you finish, blanch them again briefly.
2. 2

   Soak the bread

   Place the bread in a small bowl and pour the milk over it. Let it soak for 10 minutes, turning once, until the bread is completely saturated and soft. Squeeze out the excess milk gently. The bread should be damp but not dripping. Reserve a tablespoon of the soaking milk.

3. 3

   Pound the garlic and salt

   Place the garlic clove and a generous pinch of salt in a large mortar. Pound until the garlic is completely reduced to a paste, scraping down the sides as needed. There should be no visible pieces remaining. The salt acts as an abrasive. The garlic must disappear.

4. 4

   Add the pine nuts and walnuts

   Add the pine nuts to the mortar and pound until they form a paste. Add the walnuts in three or four batches, pounding after each addition until the nuts break down and begin to release their oils. This takes time and effort. The mixture should become a coarse, slightly oily paste. Your forearm will protest. Continue.

   A large mortar makes this work possible. If your mortar is small, work in smaller batches and combine in a bowl. A marble mortar is traditional; wood absorbs oils and retains flavors from previous preparations.
5. 5

   Incorporate the bread and cheese

   Add the soaked bread to the mortar. Pound and work it into the walnut paste until fully incorporated. The mixture will become noticeably creamier. Add the Parmigiano-Reggiano and continue pounding until the sauce is homogeneous, with a texture like coarse almond butter.

6. 6

   Add the oil

   Begin adding the olive oil in a thin stream, stirring constantly with the pestle in a circular motion. Work it in gradually, as you would make mayonnaise. The sauce should emulsify and become creamy. Add the warm water to adjust consistency. The finished sauce should flow slowly from a spoon but not be thin. Taste and add salt as needed.

7. 7

   Rest before serving

   Let the sauce rest at room temperature for at least 15 minutes before serving. This allows the flavors to marry and the texture to settle. If the sauce thickens too much, stir in a splash of the reserved milk or additional warm water. Serve at room temperature, never cold, tossed with hot pasta so the heat releases the walnut perfume.

Chef Tips

• •Fresh walnuts from the autumn harvest make the finest sauce. Stale walnuts turn rancid and bitter. Taste one before you begin. If it is sharp or musty, find better walnuts.
• •A food processor produces inferior results. The blade heats the nuts through friction, releasing bitter compounds and destroying the delicate texture. The mortar is not nostalgia. It is technique.
• •Some Ligurian cooks add a tablespoon of prescinsêua, the local curdled milk. Fresh ricotta thinned with milk approximates this. It adds a subtle tang that balances the richness.
• •This sauce is traditionally paired with pansoti, triangular pasta filled with wild herbs and ricotta. It is also magnificent with plain egg tagliatelle or potato gnocchi. Never serve it with dried pasta from a box.

Advance Preparation

• •The sauce can be made several hours ahead and kept at room temperature, covered with plastic pressed directly onto the surface to prevent oxidation.
• •Refrigerated, the sauce keeps two days. Bring to room temperature and stir well before serving. The oil will solidify when cold.
• •Freezing is possible but changes the texture. If you must freeze, do so before adding the cheese and incorporate it fresh after thawing.

Frequently Asked Questions

Nutrition Information

1 serving (about 125g)