Fortunately this year I had help. A friend of my friend Jim has a horse paddock underneath lots of oaks. Oaks that were dropping acorns something fierce. Every morning she picked up the acorns, because apparently horses get sick if they eat too many. Did I want them? Hell, yeah I did! So I met Jim and he handed over nearly 30 pounds of acorns.
Sadly, almost a third had the tell-tale hole in them that means an acorn weevil ate the nut. These acorns went outside, food for squirrels. Another portion were from an oak that set tiny acorns, not really worth bothering with. But the bulk of the remainder were acorns from California's blue oak, a "sweet" oak species whose acorns require minimal processing.
Last season I ran out of acorn flour, so I was determined to make more this time. And this time I decided to use cold water to leach out the bitterness in the acorns; last season I used boiling water. Boiling water happens to leach out some important starches in the acorns, and the resulting flour won't stick to itself as well as flour made with cold water.
This matters, because acorn flour lacks gluten—so you need every little bit of stick-to-itive-ness you can get. I also found that cold-leached flour tasted more acorn-y, and was lighter in color.
The catch? It takes many days to make cold-leached acorn flour. Here's how:
• Crack your acorns into a bucket of water, then extract them from the shells into a large bowl of water. Keeping the nuts under water helps preserve the light color—acorns oxidize and turn dark easily.
• Fill a blender half full with acorns and cover with fresh water. Buzz the hell out of them, until you have what really, really looks like a coffee milkshake. Far be it from me to suggest a truly excellent practical joke right now....
• Pour the mix into large jars (big Korean kimchee jars are great) about halfway and top off with more water. Seal the jar and shake everything up. Put the jar in the fridge.
• Every day, pour off the water, replace with fresh water, shake well, and set back in the fridge. You're done when the acorns taste boring, not bitter. The blue oaks took a week.
Now you need to dry your flour. Start by pouring everything into a colander with cheesecloth set in it. Gather the cheesecloth and squeeze it tight to extract as much water as you can.
Now spread the still-damp flour on a large rimmed cookie sheet. Break up any clumps. Blue oaks have a lot of oil in them, and you will get "acorn butter," a very light, clay-like substance that you can skim off or incorporate into the flour. I mix it in, as it has a lot of flavor. Acorn butter clumps a lot, so you will need to break it up small.
Put the cookie sheet in an oven set on "warm." Don't get the heat higher than that, or you will bake your flour, and you don't want that. A food dehydrator ought to work, too, but I don't have one.