How To Make Chestnut Flour, And What To Do With It

Little known outside of Italy and Europe, chestnut flour (farina de castagne) has been a staple crop in Northern Italy for thousands of years. At roughly four times the price of wheat flour it's a very special ingredient worth getting to know. Today we'll go over what it is, how homemade flour differs from store-bought, and how it can be used in recipes.

I knew chestnut flour could be purchased, but I didn't truly understand the historical significance until I visited Tuscany last year. Chestnut trees were everywhere near Radicondoli where I stayed.

In the fall the locals gather the nuts and bring them to a processor who dries the nuts over a wood fire, slowly smoking the nuts for weeks until their dry enough to shell and grind into flour.

In my kitchen there was a 50 lb sack of the flour in the pantry, at about 55 cents an ounce that's a roughly $450 bag of flour. Opening the bag like a kid on Christmas morning, a scene like The Amityville horror unfolded as legions of weevils escaped from the bag (which I disposed of, sadly). Needless to say, the first thing to know is that chestnut flour should be refrigerated or kept in the freezer to ward off insects and mold.

What is Chestnut Flour?

Just as it sounds, chestnut flour is made from the ground, dried seeds of the chestnut tree, known in Italy as "Alberi di Pane" (bread tree). Commercial chestnut flour is made in Italy from species of sweet chestnut (Castanea sativa) but it can also be made from American chestnut (Castanea dentata). As American chestnuts are extremely rare, most foragers in North America harvest from hybrid trees mixed with Chinese genetics.

If you harvest your own chestnuts you'll need to be able to distinguish them from bitter horse chestnuts, also known as buckeyes (Aesculus hippocastanum).

The most interesting fact to most people is that chestnut flour is essentially the original polenta. Polenta is made from ground corn, but corn is a New-World ingredient that's only been known in Italy for about 500 years.

Before corn came to Europe there was chestnut polenta, or polenta di castagne, with corn eventually taking its place. Chestnut flour is still produced, but the end product is quite different from ground corn.

How to Dry Chestnuts

Before making the flour the chestnuts must be dried. I've had success simply leaving the nuts out on a tray with a fan on them, but it's important to have good air circulation to prevent mold.

Left to dry on a tray with a fan blowing on the nuts they'll be dried in 1-2 weeks. The fastest way to dry chestnuts is to use a dehydrator which takes 3-4 days. Since the nutmeats are large, drying the nuts in an oven isn't very energy efficient and could potentially burn them.

If you really want to stay close to tradition, you could smoke the nuts in a pellet grill on the lowest heat setting for a day or two before transferring to a tray with a fan. Once the shells are bone dry the nuts can be cracked and ground.

How to Make Chestnut Flour

First the chestnuts must be cracked. The shells are brittle after drying and easily cracked with a mortar and pestle, hammer, or even by hand. To crack large amounts of chestnuts at once they can be put in a gunny sack and hit with a rolling pin or another blunt object. Any remaining test (the inner, brown fuzzy skin) is removed to prevent the flour from being bitter.

There's even electric chestnut crackers you can buy, but as the shells are the easiest to crack of any nut I've cooked I hardly think they're necessary unless you have a commercial operation.

After cracking the chestnuts are ground. As the nuts are too large for a mill I crush them in a mortar and pestle (molcajete) first to break them up. Once the nuts are broken into smaller pieces they can be ground in a grain mill or in Vitamix dry bowl.

After grinding once the flour should be sifted, with the larger particles ground and sifted again.

I've had the best results finishing my flour in a spice grinder, but even then it's not as silky smooth as the commercial flour.

How to Use Chestnut Flour

Generally speaking, the flour can be added to breads and doughs, cooked into a polenta-like porridge. As it's naturally sweet, it's great added to baked goods like cakes and pastries. While I was in Tuscany I served chestnut brownies made with ½ chestnut flour and chopped roasted chestnuts. They're to die for.

Since it contains no gluten, if you're making bread you'll want to add no more than 30% of the total weight of flour to ensure it rises properly.

Homemade vs Store-Bought

The chestnut flours I've purchased online are velvety smooth with a texture like powdered sugar. Cooking with them reminds me of Korean acorn starch in that it absorbs less water than cornmeal.

The flour I make at home is more coarse and is noticeably less sweet, likely due to a sweeter variety being used to make the commercial flour. For most purposes, the finer you can get your flour to be, the better it will perform.

Homemade flour is best for things like polenta, or adding to wheat breads or quick breads. As it's slightly less sweet, it's also easier to serve with savory dishes. Commercial flour is what you'll want to make pasta and the famous necci (pancakes / crepes), pasta and gnocchi as they can be brittle made with homemade flour.

In short, homemade chestnut flour can be used in recipes calling for cornmeal, and smooth commercial flour can be substituted for all-purpose flour.

Chestnut Flour Recipes

There's a number of traditional recipes using chestnut flour which can be savory or sweet. Any of the sweet recipes pair perfectly with chestnut honey which has a rich, unique flavor. Here's a few of my favorites I've made over the years.

• Necci: Tuscan Chestnut Pancakes / Crepes

Probably the easiest to make, these are simply crepes. Naturally sweet, they're traditionally served with ricotta cheese filling but can also be used like cannelloni pasta tubes or in any recipe calling for crepes.

• Chestnut Polenta / Polenta di Castagne

While it might sound like a dish dish to serve with ragus or braised meats, the natural sweetness of the nuts puts the polenta firmly in the sweet realm unless mixed with cornmeal.

It's traditionally served with ricotta, and makes a delicious, filling meal for breakfast, brunch, or light summer dessert. Smooth as velvet, nutty and sweet, the cooled slices drizzled with chestnut honey and ricotta cheese is novel, delicious, and addictive.

• Chestnut Pasta

One of the most interesting recipes I've made over the years as it defies the conventional 30/70 rule of how much wheat flour can be diluted by alternative flours. Up to half of the wheat flour can be substituted with chestnut flour.

• Chestnut Gnocchi

While you could technically make fresh gnocchi with a puree of nuts mixed with potatoes, the traditional dough is simply a pasta dough. Just like potato gnocchi, the dough is rolled into ropes, cut into pieces and rolled off a gnocchi board or the tines of a fork to give them the traditional ridged appearance.

They have a firm texture of pasta and the subtle sweetness means they pair well with wild game like boar, duck and venison.

• Castaggnaccio, Cakes and Breads

The most famous dessert besides the Monte Bianco (made from a puree of fresh nuts) is Castagnaccio, a sort of firm, hard cake studded with grappa-soaked raisins and flavored with rosemary and orange peel.

There's also regional variations nearly identical to the acorn flour torte in my book which is leavened with whipped eggs pictured above. Chestnut flour could be substituted for a similar, slightly sweeter effect. There's a link to my recipe below.

In closing, I'm including the method I use to make chestnut flour below for posterity, but it's mostly for die-hard chestnut foragers. If you're curious about cooking with it, I recommend starting off buying Italian chestnut flour as it's much easier to work with.

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