Set a colander or fine mesh strainer over a large bowl. Line with a double piece of cheesecloth, nut milk bag, or thin kitchen towel.
Pour the milk and cream into a large saucepan. Stir in the salt. Bring to a simmer over medium heat, stirring occasionally. Stir in the lemon juice and continue to simmer for 1 to 2 minutes, until the mixture curdles.