In a separate mixing bowl, beat eggs until fluffy. Add sugar and cream; beat together. Continue beating egg mixture while slowly adding flour and cocoa.
Thoroughly dissolve soda in water (or coffee); add to batter and mix.
Pour batter into a buttered and floured 9 x 13" pan. Bake at 350℉ for 40 minutes, until toothpick comes out clean.
Notes
*Cream must be sweet cream either naturally soured or with lemon juice added to sour it; cultured sour cream will not have the same results.