Castagnaccio (Tuscan Chestnut Cake)

A flat, dense, moist cake of chestnut flour, water and olive oil, scattered with raisins, walnuts, pine nuts and rosemary. Chestnut flour is sweet enough that it needs barely any sugar.

Untested: not yet made in this kitchen. It is here as the showcase for one flour in the Flour section and is adapted from the source named in the Notes.

Ingredients

• 3¾ cups (400 g) chestnut flour
• 3 tablespoons (45 g) sugar
• 2½ cups (625 ml) cold water
• 3 tablespoons olive oil, divided
• ½ cup (100 g) golden raisins
• ¼ cup (20 g) walnut pieces
• ¼ cup (35 g) pine nuts
• A sprig of fresh rosemary, leaves picked
• A pinch of salt

Directions

1. Batter. Mix the flour, sugar and salt, adding the water a little at a time to make a lump-free batter that runs off a spoon like pancake batter. Chestnut flours vary, so adjust the water. Stir in 2 tablespoons of the oil and rest at least 30 minutes.
2. Prepare. Heat the oven to 350 °F (180 °C). Soak the raisins 15 minutes and drain. Line a 12 × 8-inch (30 × 20 cm) dish with parchment.
3. Fill. Pour in the batter no more than ⅓–½ inch (1–1.2 cm) deep. Scatter the raisins, walnuts, pine nuts and rosemary over it and drizzle with the remaining oil.
4. Bake about 30 minutes, until small cracks appear on top. Do not overbake.
5. Cool in the pan.

Notes

Source Adapted from Emiko Davies, “Tuscan Chestnut Cake (Castagnaccio),” Food52 (read through the Wayback Machine).

A correction to the source’s numbers Several volumes and weights disagree: half a cup of raisins is usually about 75–80 g, not 100 g; a quarter cup of walnuts about 25–30 g, not 20 g; and 3 tablespoons of sugar about 37 g, not 45 g. Weigh, and use the source’s grams.

Why this flour Chestnut flour is naturally sweet and gluten-free, and was for centuries a staple of the poor in the Apennines. With only water and oil it bakes into a dense, cracked-top cake. Davies notes that “cake” is a poor translation.

Keeping A few days airtight at room temperature. Do not refrigerate — it turns hard and rubbery. Chestnut flour itself goes stale; buy it fresh after the autumn harvest.

Safety Contains tree nuts (walnuts, pine nuts).

Gluten-free by ingredient: safe for coeliac disease only if every ingredient — flour, starch, baking powder — is labelled gluten-free. Naturally gluten-free flours are often contaminated with wheat in milling.

The Flour section of the Food site covers the history, the science, milling, label systems and every flour used here.