Mix cocoa powder with 1/2 of the sugar. Combine the milk and cream in a medium saucepot and whisk in the cocoa/sugar mix to dissolve. Heat slowly to a simmer.

In a medium bowl, whisk together the egg yolks and the other 1/2 of the sugar.

Temper the eggs by mixing in 1/2 cup of the hot milk/cream to heat them up, but not cook them. Mix the eggs back into the pot with the hot milk/cream. Cook over a low flame until the mixture begins to thicken. Do NOT boil or you may end up with chocolate scrambled eggs.

When thick, pour the custard mix through a strainer into a clean bowl. Cool the bowl in an ice bath, stirring occasionally to speed up the process.

When cool, mix in the vanilla and put the bowl in the refrigerator. Chill thoroughly before freezing in your ice cream maker.

When making the ice cream, add in the peanut butter at the end of the churning process. I really like mine with lumps of peanut butter, rather than spread through the ice cream, so I mixed most of it into the container after I took the ice cream out of the freezer bowl. I also froze the peanut butter in lumps hoping it would help it stay separate while I mixed it in. Freeze at least 4-5 hours before serving.