Melt butter in large sauce pan, add milk, sugar and cocoa powder. Bring to medium boil and boil for 1 minute. Any longer and the sauce will harden too much when cookies set. Any shorter and the cookies may not harden enough.
Remove from heat and add rolled oats and coconut. (I usually premix the coconut and oats). Mix well with wooden spoon and drop onto parchment or wax paper. You decide on the size of cookies you want. These cookies take about a 1/2 day to a day to set depending on the size.