In a small pot add the milk and sift the cocoa over it. Add the sweetened condensed milk and salt then cook on low, whisking until smooth.
When it starts to steam, remove it from the heat, pour it into a bowl through a fine mesh sieve and set in the fridge for 2 hours to chill.
You can speed this up by placing it in the freezer for about 20 minutes, but don’t let it freeze and stir it at the 10 minute mark.
Once it’s cool, pour in the cold heavy cream and vanilla.
Use a hand mixer or a stand mixer fitted with the whisk attachment to whip the mixture to medium peaks. The mix will be thickened and airy.
Pour into an airtight container or into an open container and seal it with plastic wrap.
Freeze for about six hours. If the ice cream is too difficult to scoop, let it warm up for about 5 minutes on the counter.