In a bowl, stir together the sourdough starter, kefir, water and flour to combine. Cover and set aside in a warm place for 8-12 hours.
After more than 8 hours, melt butter in a small saucepan. Add in sucanat and cocoa powder, stirring until combined. Allow the mixture to come to a boil, immediately remove from the heat and add the vanilla and salt, mix together. Allow this to cool until it's lukewarm.
Preheat oven to 350 degrees F. Grease and 8x8 or 9x9 pan and set it aside
Beat egg into the cooled chocolate mixture. Add chocolate mixture to the bowl of starter-flour mixture and work in until smooth and combined. Quickly whisk in baking soda until evenly mixed. Pour batter into prepared pan. Bake in preheated oven for 30-35 minutes or until a toothpick inserted in the center comes out clean. Meanwhile, make the frosting recipe. Pour warm frosting over the slightly warm cake, spreading out evenly, if using chopped pecans, sprinkle those on top.
2 tbsp. butter
2 ounces semi-sweet chocolate chips or chocolate chopped up
2 tbsp. honey or maple syrup
1/4 tsp. vanilla extract
Pinch of unrefined sea salt
4 tbsp. kefir or buttermilk
1-1 1/2 tbsp. unbleached all-purpose flour
Melt butter and chocolate in a double-boiler over simmering water. Stir in honey or maple syrup to dissolve, followed by vanilla, salt and kefir. Add in the flour, a little at a time, until thickened to your liking. Keep in mind that the frosting will thicken up a little more as it cools.