Things You\’ll Need
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Filtered water or spring water
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Nut-milk bag or cheesecloth and fine-mesh sieve
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Rubber spatula
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Food dehydrator and nonstick drying sheet
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Parchment paper and sheet pan (optional)
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Spice grinder
Making chestnut flour requires finesse. Unlike other nut flours, such as almond, that you can simply grind into a coarse meal and call it a day, you have to coax chestnuts into a fine flour from start to finish. But when you process chestnut flour to a dry, silky consistency, you can use it in dishes too refined for coarse, mealy flours, such as gnocchi, crepes and clafoutis.
Peeling and Preparing
Step 1
Slice each chestnut in half vertically, from the pointed tip to the rounded bottom. A sharp, heavy chef's knife works best. Work in 1-pound batches of unshelled chestnuts.
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Step 2
Bring a few quarts of water to a boil in a large pot; you need enough water to cover the chestnuts by at least 1 inch. Add 1 pound of halved chestnuts to the boiling water.
Step 3
Blanch the chestnuts for 7 1/2 minutes and drain them in a colander under cold running water. Let the nuts drain in the colander for a few minutes and transfer them to a bowl.
Step 4
Drop the chestnuts from their shells into a separate bowl. Extract the nuts that don't fall out readily with the tip of a paring knife.
Step 5
Cover the chestnuts with filtered water or spring water and let them soak for 10 to 12 hours.
Processing
Step 1
Transfer the chestnuts and the water to a blender or food processor. Process the chestnuts until smooth; work in batches, if necessary.
Step 2
Scrape the pureed chestnuts from the blender to a nut-milk bag set over a bowl. You can also pour the chestnut puree into a sieve lined with two or three layers of cheesecloth set over a bowl.
Step 3
Let the chestnut milk drain into the bowl for about 5 minutes; then press the solids using a rubber spatula. Wring the remaining chestnut milk from the bag or cheesecloth. Store the chestnut milk in an airtight container for up to three days in the refrigerator.
Step 4
Scrape the chestnut pulp onto a nonstick drying sheet and spread it in an even layer, no thicker than 1/4-inch thick, using a spatula. Dry the pulp in a food dehydrator for 24 hours at 105 degrees Fahrenheit.
Alternatively, spread the chestnut pulp in an even layer on a sheet pan lined with parchment paper. Dry the pulp in the oven on the lowest setting for 24 hours or until it's completely dry; use a towel or oven mitt to keep the oven door propped open about 1 inch.
Step 5
Transfer the dry chestnut pulp to a spice grinder and process it into a fine powder. Store chestnut flour in the refrigerator for up to three days.
Tip
Replace up to 20 percent of the wheat flour in any recipe with chestnut flour.
