Place a rack in the center of the oven and preheat to 350 degrees. Spray an 8" square cake pan with cooking spray or line with parchment paper and set aside.
Melt butter in a medium-sized saucepan over medium-low heat then add chocolate chips, stirring constantly until melted. Remove from heat then set aside to cool slightly.
Whisk together eggs, sugar, vanilla and salt in a large mixing bowl until completely combined. Sift flour, cocoa powder, baking powder and salt over the top of the egg mixture then stir to combine.
Add the chocolate mixture to the egg mixture then stir until completely incorporated. Fold in walnuts, if desired.
Transfer the batter into the prepared pan and let rest 30 minutes in the refrigerator to allow the einkorn to fully hydrate. Bake 23–25 minutes until firm in the center. Cool on a wire rack, slice and serve. Enjoy!
Notes
Allow the chocolate mixture to cool slightly before you add it to the rest of your ingredients. Otherwise it will cook the eggs in the batter.