I grew up in the San Joaquin Valley of California where the oak trees were plentiful and my Portuguese great-grandmother made acorn flour every year. I'm sorry I don't have photos, but I've done this a hundred times - here is our process:
- The larger acorns are the best - but any will work - some have more tannin than others
- Lay the acorns out on a baking sheet
- Put them in a hot oven (425) for a few minutes. Listen. When they begin to pop, pull them out. The steam from the nut will crack the shells and they will literally just fall off. If the nut is cooked, that's ok.
- Put the nut in the food processor (easier than hand grinding these days but you CAN use a hand grinder)
- Put a little water in (doesn't matter how much) and grind to a nice meal
- Put some cheese cloth in a collander and put the meal in the collander
- Run cold water through the meal a few times, tasting each time
- When it's no longer bitter, it's ready. This really only takes 5-10 minutes.
- Drain the meal and press out the water
- Spread the meal on the same baking sheet and put in a 325 oven
- Dry it (you can also put it in a dehydrator
- Break it up once dry and either use it as a hot cereal for breakfast or grind it fine in a flour mill to make wonderful golden flour - gluten free !