One of my favourite food books is Americas Test Kitchen’s The Science of Good Cooking. The section on freezing shares many phrases with the steel manufacture section of my materials science books from engineering school. “Nucleation”, “crystal growth”, “supercooling”; steel and ice are very similar at the microscopic level.
But unlike steel and ice, we want ice cream to be soft. So when its made, we use whatever cheats we can to stop a solid, hard mass forming. Sugar not only sweetens, but forms a super slippery sugar solution between ice crystals. Air bubbles and fat molecules also help separate ice crystals, while a rapid freezing time ensures those crystals are as small as possible (see Kurt’s liquid nitrogen version). For more on the science of ice cream see Clarke, 2003, “The Physics of Ice Cream”
Americas Test Kitchen’s recipe for homemade chocolate ice cream applies these principals and uses only cream instead of a milk-cream mix: no churning required! My flat has no ice cream maker (three toasted sandwich presses though) so this was a revelation to me, and led to enthusiastic testing of new flavour bases: mint-chocolate, passionfruit, banana, peanut butter, boysenberry, pretty much anything in a two metre radius of my kitchen got turned into ice cream. Two months (and 4kg on the bathroom scales) later, the recipes below are mine and my tasters’ favourites. Feel free to apply the general idea and make up your own bases with your own favourite flavours, and let us know how it goes in the comments below!