Blackout Cake Recipe

Yield:½ sheet pan sized cake of 3 layers, which can be cut into 24 triangular pieces.



Onyx filling and glaze


Onyx (melted to 110°F):

2 lbs

Heavy cream:

16 oz

Light corn syrup:

1 tbsp





Chocolate cake mix:

Make three ½ sheets


  •     Use chocolate cake mix to make three ½ sheet pans of chocolate cake.
  •     For individual 3” cakes, cut ½ sheet pan-cake layers with 3” round cutter. You should get 19 (3” pieces) per ½ sheet pan.
  •     Reserve the trimmings and create cake crumbs from them by crumbling them lightly with your fingers.
  •     Lightly whisk Onyx with heavy cream (and corn syrup) until a pudding like consistency is achieved.
  •     Pipe or pour onto centers of cake layers, and spread to edge for 1/8” thick layer.
  •     Stack layers. Refrigerate until firm.
  •     Place stacked/filled cake layers on rack over clean sheet pan.
  •     Warm filling/glaze gently in microwave or over water bath until desired viscosity for glazing. Pour glaze over cakes. Even the top layer of glaze with offset spatula.
  •     Cover sides of cake with cake crumbs.
  •     Serve with ice cream or whipped cream and berries.

*Note: If you want to slice triangular portions from full or ½ sheets – coat stacked cake top with Onyx filling/glaze, coat with cake crumbs, cover with sheet of parchment paper, flip cake over onto another sheet pan, coat (bottom, now) top with Onyx filling/glaze, and then cover with cake crumbs. Refrigerate well before slicing. Slice 3 x 4 into 12 rectangles, and then slice each rectangle in ½ diagonally to make 24 triangles.