Add the sweetened condensed milk, heavy cream, cocoa powder vanilla extract and salt to the bowl of a stand mixer. Using the wire whisk attachment, beat on a low speed until combined. Slowly increase to a medium-high speed, and beat until soft peaks just begin to form, scraping the sides of the bowl as necessary.
Pour the ice cream mixture into an 8 ½ x 4 ½ inch loaf tin. Freeze for a minimum of 4 hours, or until frozen through.
Notes
A large mixing bowl and hand held electric beaters can be used in place of a stand mixer.
Beating the mixture until soft peaks just begin to form is the key to getting the perfect frozen texture.
Chocolate chips or chocolate chunks could be folded through the mixture just before freezing.