A childhood belief about milk

At my friend's house one day, we suddenly got an idea to go out and collect acorns. My friend put them in a bowl, along with some grass and water and began mashing it with a stick. And somehow eventually the water turned white. My friend told me it was milk, but even so i didn't have the heart to taste it. From then on I believed acorns, grass and water made milk (why this logic? because cows eat grass and they produce milk). I remember spending a day with a bowlfull of grass and water, but no acorns were at hand. I spent the afternoon mashing it and leaving it in the sun for awhile, till my sister came out and asked me what i was doing. 'Making milk,' I replied. 'But it's not working. I don't have any acorns.'