In a large mixing bowl add the starter, evaporated milk and flour, cover loosely with a clean towel and allow to sit overnight.
The next morning place the beets, eggs and vanilla in a blender container and process until combined and smooth; set aside.
Cream the butter and sugar add in the beet and egg mixture; add starter.
Combine the flour, salt, baking soda and cocoa; add to batter mixing well; fold in crème fraiche.
Pour into a 13 x 9 inch pan that has been greased and floured. With a tablespoon drop marshmallow cream over the cake and swirl mixture with a knife. Bake in preheated 375 degree oven for 30 to 35 minutes or until the top springs back when lightly touched. Allow cake to stand 10 minutes while preparing frosting.
Place the sugar, and vanilla in large mixing bowl, melt together the butter, nutella and 6 tablespoons milk; pour melted ingredients over the sugar and beat until combined and spreading consistency adding additional milk if needed. Spread quickly and carefully over cake.