The lowly meat grinder..
Go through one course die, one medium die, and then zing it through the food processor.
Of course, the higher the water content and lower fiber content you have, the easier and smoother it will be.
But the best machine for turning solids to absolute smooth creams?
I haven't seen one here in N. America, but were common in European pastry shops. Again very low tech, consisting of two rotating marble rollers and adjusting the gap between the rollers to regulate how fine you want the mix to be. Same principle for making chocolate from whole cocoa beans, or marzipan from whole almonds, and making various nut butters.