In a small sauce pan, over medium to medium low heat, start melting butter. When butter is almost melted, add chocolate chips. When the chocolate starts to melt as well, add buttermilk. Slowly stir until all melted and smooth.
Preheat water in the double boiler over medium heat. Add chocolate, 2 Tbsp of water, butter and vanilla extract. Let it start melting and then stir with a silicone covered whisk until all melted and smooth. Take off heat and set aside.
In a small, heavy sauce pot, over medium-low (to low) heat, whisk egg yolks, 2 Tbsp of water and 3 Tbsp of sugar together. Cook stirring slowly but constantly, until the mixture reaches 160 degrees (F). This could take up to 10 minutes but don't walk away or you will cook your eggs. Take off heat.