Ingredients:

  • 1 ¾ cups (210 g) All-Purpose Flour, sifted
  • 1 ¾ cups (350 g) Granulated Sugar
  • ¾ cup (75 g) Unsweetened Cocoa Powder, Dutch-processed recommended
  • 2 teaspoons Baking Soda
  • 1 teaspoon Baking Powder
  • 1 teaspoon Kosher Salt
  • 2 Large Eggs, room temperature
  • 1 cup (240 ml) Buttermilk, room temperature
  • ½ cup (120 ml) Neutral Oil (e.g., vegetable, canola)
  • 2 teaspoons (10 ml) Vanilla Extract
  • 1 cup (240 ml) Hot Water or Hot Coffee
  • 1 (14 oz / 396 g) can Sweetened Condensed Milk
  • 1 cup (175 g) Semi-Sweet Chocolate Chips
  • 2 tablespoons (30 g) Unsalted Butter
  • 1 teaspoon (5 ml) Vanilla Extract (for filling)
  • Pinch of Salt (for filling)
  • 4 oz (115 g) Cream Cheese, softened
  • 1 (7 oz / 200 g) jar Marshmallow Fluff (Marshmallow Creme)
  • ½ cup (120 ml) Heavy Cream, cold
  • ½ teaspoon (2.5 ml) Vanilla Extract (for topping)
  • Chocolate Shavings or Zest (for garnish)

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and lightly flour the 9x13 inch baking pan.
  2. In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt (dry ingredients).
  3. In a separate medium bowl, whisk the eggs, buttermilk, oil, and 2 teaspoons of vanilla extract (wet ingredients) until just combined. Pour the wet ingredients into the dry ingredients and mix on low speed until the batter is smooth.
  4. Carefully pour in the hot water or coffee and mix until the batter is thin and smooth. Pour the batter into the prepared pan. Bake for 30–35 minutes, or until a skewer inserted into the center comes out clean. Let the cake cool on a rack for 15 minutes in the pan.
  5. While the cake is still warm, use the round handle of a wooden spoon or a thick skewer to poke deep holes evenly across the entire surface, spacing them about 1 inch (2.5 cm) apart.
  6. Prepare the filling: Combine the condensed milk, chocolate chips, butter, 1 teaspoon vanilla, and a pinch of salt in a heatproof bowl. Microwave in 30-second intervals (or use a double boiler) until the chocolate is fully melted and the mixture is smooth, thick, and glossy.
  7. Slowly pour the entire chocolate filling mixture over the warm cake, ensuring the liquid pools into every hole. Use a spatula to gently spread any excess over the surface. Cover loosely and chill for a minimum of 2 hours, or until the filling is fully set and firm.
  8. Prepare the topping: In a chilled bowl, whip the ½ cup of heavy cream until stiff peaks form. Set aside.
  9. In a separate bowl, use an electric mixer to beat the softened cream cheese until completely smooth. Add the marshmallow fluff and ½ teaspoon vanilla; beat until well combined and airy.
  10. Gently fold the whipped heavy cream into the marshmallow/cream cheese mixture. Spread the marshmallow topping evenly over the chilled, filled cake.
  11. Garnish with chocolate shavings. For an authentic hot chocolate look, optionally use a kitchen torch to lightly toast the surface of the marshmallow topping until golden brown. Slice and serve chilled.