Butter and flour 2 - 8" round pans. Preheat oven to 375.

In a small saucepan, over medium heat, combine butter, water and cocoa powder. Bring to a boil. Reduce heat and simmer for 2 min - while stirring. Remove from heat and let cool. 

In your stand mixer or large bowl, combine the eggs, sour cream, sugar, and stevia. 

In a medium bowl combine the flour and baking soda. 

Gradually add the flour mixture to the egg mixture. Mix to combine.

Slowly add in the cocoa mixture. Mix until smooth.

Fold in the chocolate chips. 

Divide equally into the two pans and bake for 20 - 25 min. 

After the cake has cooled, if serving, dust with powdered sugar and serve. If freezing, wrap tightly with plastic wrap and place in an airtight freezer bag (will keep for 6 months in the freezer).