1/2 gallon raw whole milk
1 pint heavy cream
3/4 cup plain yogurt (any kind), whisked until smooth
1 1/4 cups sugar
1. In a large saucepan, boil the milk and cream, over medium-high heat the first 2 to 3 minutes, then over medium heat until reduced by half, 15 to 20 minutes.
2. Add the yogurt, which will cause the milk to curdle, reduce the heat to low, and cook, about 10 minutes. Increase the heat to medium and continue to cook until the whey from the curdled milk has almost evaporated, about 15 minutes. Add the sugar and cook, stirring, until the mixture starts to pull away from the sides of the pan, about 10 minutes.
3. Meanwhile, lightly grease a 6- to 8-inch round container, making sure it has a secure and tight fitting lid. Have ready a large pot with ice cold water and ice cubes. As soon as the cake mixture is done, transfer it in to the greased container and quickly secure the lid. Then, carefully, place the container in the ice cold water, which will instantly start to cool the cake from the outside. Make sure no moisture gets inside the cake. Allow the cake container to sit in its ice bath 30 to 45 minutes, and add more ice if needed.
4. Carefully remove from the ice bath and bring to room temperature. Invert the cake onto a serving dish and serve as you would any cake.