In a large, heavy saucepan, combine the heavy cream and one cup of sugar and bring to a simmer over medium heat.
In a large bowl, whisk egg yolks and remaining 1/4 cup of sugar.
Remove the cream mixture from the heat and drizzle a small amount into the yolks, slowly, and whisking constantly to keep the eggs from curdling. Do this a few more times to warm up the yolks before pouring the yolk mixture back into the cream, whisking constantly.
Cook over low heat until the mixture is thick enough to coat the back of a spoon.
Mix in the chocolate and stir until melted.
Remove from heat.
Strain the mixture and whisk in the buttermilk, vanilla, and salt.
Cool completely and freeze in your ice cream maker. (I found that this ice cream was still too soft after the ice cream was done. I transferred it to another container and froze it for another few hours and it was perfect!)