In a large bowl, whisk together the sifted cocoa powders, the granulated sugar and the light brown sugar. Whisk to combine.
Add in the kosher salt and whisk again to combine.
Add in the milk and whisk again to combine until the coca powders and sugars have dissolved.
Pour in the heavy cream and vanilla. Whisk again until just combined. Cover the bowl with plastic wrap and refrigerate for at least two hours or overnight.
After 2 hours, turn the ice cream maker on and follow the manufacturer’s instructions. I use cuisinart. If using cuisinart, pour the liquid ice cream into the frozen freezer bowl and let the machine mix it for 15-20 minutes until the ice cream is thick and creamy. Once it starts pushing out of the top of the machine, if using cuisinart, it’s done.
Transfer to a freezer safe ice cream container or a 9x5 loaf pan and cover with plastic wrap and then aluminum foil. Freeze for at least 2 hours. You can of course eat it right out of the machine but it will be very very soft.