Mostillo de Nueces (Castilian grape must and walnut preserve)

Grape must thickened with flour and spiced with cinnamon, packed with walnuts: the preserve of the Castilian harvest season

Origin: Castile and La Mancha, Spain

From the journey of Walnut.

Mostillo is one of the most honest expressions of the Spanish autumn: a preserve made in the hours immediately after the grape harvest, when the fresh pressed juice (mosto) is still sweet, unfermented, and almost luminous in colour. The preparation is ancient and practical: grape must, thickened with flour and spiced with cinnamon and aniseed, is cooked to a dark, dense paste and poured over; or packed with; walnuts harvested from the same autumn that brings in the grapes. It sets as it cools into a firm, sliceable block that keeps through the winter without refrigeration. Mostillo is documented in Castilian and Manchegan cookbooks from the 16th century onward, though the preparation itself is considerably older, descending directly from the Roman and Moorish traditions of grape-must preservation (the Romans made a similar preparation called defrutum, and the Moors brought the refinement of cinnamon and aniseed into the Spanish kitchen). In the walnut-growing regions of Extremadura and Castilla-La Mancha: the same provinces that supplied the conquistadors and colonists who sailed to the New World; mostillo was a staple winter food: energy-dense, non-perishable, and made from the two most abundant autumn harvests of the Spanish interior. The walnuts in mostillo are the descendants of Roman-planted Juglans regia trees; they are the same genetic stock that would eventually be carried to New Spain. When Hernán Cortés's men, mostly Extremadurans who had grown up cracking walnuts for the winter store, arrived in Mexico and planted the trees they knew from home in the gardens of the missions and haciendas of New Spain.

Ingredients

Base

  • 1 litre fresh grape must (freshly pressed grape juice, unfermented), or use good-quality red grape juice as a substitute
  • 100 g plain flour (all-purpose)

Walnuts

  • 150 g walnut halves or large pieces

Spices

  • 1.5 tsp ground cinnamon
  • 0.5 tsp ground aniseed (or 1 star anise, finely ground)
  • 1 strip lemon zest (no white pith)
  • 0.25 tsp fine sea salt

Method

  1. Whisk the flour into 200 ml of the cold grape must until completely smooth and no lumps remain. Set aside. Pour the remaining 800 ml of grape must into a medium heavy-bottomed saucepan.
  2. Add the cinnamon, ground aniseed, lemon zest, and salt to the saucepan. Bring to a gentle simmer over medium heat, stirring occasionally.
  3. Once the must is simmering, pour the flour-must mixture into the pan in a steady stream, whisking constantly to incorporate. The mixture will begin to thicken almost immediately.
  4. Reduce heat to low. Cook, stirring constantly with a wooden spoon or spatula, for 20–25 minutes until the mixture is very thick, dark, and pulls away from the sides of the pan when stirred. It should have the consistency of a very thick polenta.
  5. Remove the lemon zest strip. Fold in the walnut pieces, distributing them evenly through the paste.
  6. Pour or spoon into a lightly oiled shallow dish, loaf tin, or onto a sheet of baking parchment. Smooth the top. Allow to cool completely at room temperature; the mostillo will firm up considerably as it cools and sets into a dense, sliceable block.

Notes

Fresh grape must (mosto) is available from wineries and specialist shops during the October harvest season; outside this window, good-quality red grape juice (not from concentrate, with no added sugar) is the best practical substitute, though the flavour will be lighter and less complex. Mostillo keeps wrapped at room temperature for up to two weeks and refrigerated for up to a month. Serve sliced thinly alongside manchego cheese, cold cured meats, or as a sweet-savoury accompaniment to roast game. Some Castilian recipes add a handful of dried figs or pine nuts alongside the walnuts.

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