Unusual Ingredient of the Week - Chestnut Flour

Sometimes an ingredient has been sitting for so long in your cupboard that it becomes as familiar as that little spider that made its' home in the vent in the bathroom or the pile of bricks on the draining board that have been sitting there, just waiting to be used, for months now. You look at these things that might seem out of place to other, more anally retentive people, as if they were old, comfortable friends: you don’t want to think too deeply so you just discuss the weather with them.
Apparently though, these things serve a purpose. The spider is to catch unsightly insects, the bricks are to fill the gap in the wall where the new window was fitted over a year ago and the chestnut flour is to cook with.
Of course, as this is an article on cookery, and unusual cookery at that, I won’t bore you with my noted lack of housekeeping skills, nor my husband’s lack of DIY motivation. Instead I will discuss that most Italian of ingredients, chestnut and more importantly, chestnut flour.
Most of us have had roasted chestnuts at some point in our lives. You may have bought them from a street vendor and burnt your fingers trying to peel them, maybe you’ve been lucky enough to have tasted the delicate, sweet/salty fudgyness of Marron Glaces or, like me, gathered them up down a country lane and then roasted them on an open fire . They have such a distinctively rich, indulgent flavour that you can see why Chestnuts have strong connotations with Christmas.

Originally considered peasant food, they are very high in carbohydrates and incredibly filling when milled and turned into flour. The chestnut is still very important to Italian Culinary culture and each year they celebrate the Chestnut Harvest with a festival.
Chestnut Flour is unlike most other flours in that it doesn’t contain the gluten content found in normal grain-based flours so is ideal for gluten intolerant guests (although when used in cookery, the chestnut flavour is predominant and I wouldn’t recommend using it for making, say, an Angel Cake or some other light confectionary due the mealiness of it).
I bought a bag of Chestnut Flour, which I had to import from France for a ridiculously large amount of money (but I did get a free oven glove so I suppose there’s an upside to it), a couple of years ago when we were heavily into our Italian phase of cookery. I was making Risotto like there was going to be an Arborio famine and my husband experimented with homemade pasta and ravioli. I used the chestnut flour to make some pasta. After kneading the dough for a couple of minutes, it rapidly became clear to me that I would need to enlist someone burlier than me to finish the job. Let me elaborate. Kneading chestnut pasta dough is somewhat like kneading clay. It is very, very thick indeed. I suppose that the lack of gluten means that it needs that much longer to get it going. After about forty five minutes of kneading and enough pummelling to put a Swedish Masseuse to shame, my husband, bowed but undefeated, had produced a glorious ball of pasta dough that contained his blood, sweat and tears. We ran it through the pasta machine (turned by hand, not by motor), turned it into Chestnut Tagliatelli, boiled for a couple of minutes and then tossed it in a delicate Alfredo sauce that had been punctuated with tiny fresh vine tomatoes cut in half. The taste was undeniably chestnut. It had a mouth-filling taste of the earth that was unique.
When you taste chestnut used in this way, it is hard to imagine how some sugar can turn it from an earthy savoury dish into a much-desired sweetmeat. So, after two years of the partially used bag of flour sitting in my cupboard, I decided to turn it into just that. A sweetened delicacy – a chestnut flour cake, known famously in Italy as a Castagnaccio.
Castagnaccio has evolved over time from a cake originally carried by Roman Soldiers, many hundreds of years ago, when they were exploring and conquering unknown parts of the Roman Empire. It has great cultural significance and is still made to this day, albeit in a slightly more palatable form.
This was probably the most unusual method for making a cake that I have ever come across. It doesn’t contain eggs, or butter or a rising agent or vanilla extract. Just three ingredients: Chestnut Flour, Olive Oil and Sugar, all mixed together with a litre of cold water. The batter is then studded with nuggets of raisins, shards of fresh rosemary and pine nuts. The raisins sink to the bottom, but the nuts and herbs striate the top of the cake. You can imagine how beautiful this looks when you first remove it from the oven, all golden brown, the nuts and rosemary toasted. The cake itself is a similar texture to a fresh chestnut, almost marzipan-like and tinted a pale, pale lilac. It is a curiously lovely cake that can be served with some fresh ricotta or spread with butter. Incredibly simple to make.
500g Chestnut Flour
75g Caster Sugar (I actually used 100g because I prefer to enhance their natural sweetness)
3 tablespoons Olive Oil (I used regular cooking olive oil, fairly cheap) plus 2 for oiling the tin
1 Litre Cold Water
50g Pine Nuts
75g Sultanas soaked for 10 minutes in warm water (I used 100g because that finished the bag up)
2 Tablespoons freshly chopped (roughly) Rosemary
You can also add some orange zest to the batter but I didn’t have any oranges in the house.
Preheat the oven to 190c.
Grease a cake tin, round or square, no smaller than 8” dia/square. The smaller the tin, the deeper and therefore more denser the cake will be. I used an 8” springform tin. Great well with 2 tablespoons of olive oil.
Mix the Chestnut Flour and Sugar in a bowl. Stir in the 3 tablespoons of olive oil. The flour/sugar mixture will drink this up. Gradually pour in the litre of water, beating all the time with a wooden spoon until lump-free (you may need to use your whisk to get rid of any pesky lumps but there shouldn’t be many).
Pour into your oiled tin.
Sprinkle the (drained) Sultanas, Pine Nuts and Chopped Rosemary onto the top of the cake. The Sultanas will mostly sink to the bottom as the cake cooks.
Cook for anything between 45 minutes to 1 ½ hours depending on the size of your tin (working on the basis that the large the tin, the shallower the cake, so the shorter the cooking time). A skewer will not come out clean even when the cake is cooked so you have go by sight. It will be a rich golden brown, the nuts and rosemary tinged bronze, and it will have started to come away from the edges. It will be springy to the touch.
Leave to cool. Once cooled, the cake will have stabilised into a fudge-like texture and will be ready to served, dusted with icing sugar if wanted, some fresh ricotta or spread with butter.

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