Preheat your oven to 400 degrees Fahrenheit. Prepare your baking pan by greasing it or using parchment paper to prevent the cake from sticking. A jelly roll pan or a 9×13 baking dish works perfectly for this recipe.
In a large mixing bowl, combine all-purpose flour, granulated sugar, and baking soda. Use a whisk to blend these dry ingredients thoroughly. This ensures an even distribution of the baking soda, which is crucial for the cake to rise properly.
In a medium saucepan, melt the butter over medium heat. Add the canola oil, unsweetened cocoa powder, and water. Stir the mixture continuously until it comes to a boil. Once boiling, remove the saucepan from the heat and carefully pour this chocolatey mixture over the flour mixture in the bowl. Stir until just blended, ensuring there are no dry pockets of flour.
Add the buttermilk, beaten eggs, and vanilla extract to the bowl. Mix everything together until combined, being careful not to overmix. You want the batter to be smooth and well incorporated.
Pour the batter into the prepared baking pan, spreading it evenly with a spatula. Place it in the preheated oven and bake for about 20 minutes or until a toothpick inserted into the center comes out clean. The cake should be set and slightly springy to the touch.
While the cake is baking, prepare the frosting. In a mixing bowl, combine the softened butter and Dulce de Leche. Mix until creamy and well blended. Gradually add the powdered sugar, one half-cup at a time, mixing well after each addition.
Once the frosting is smooth, add the additional vanilla and enough milk to reach your desired consistency. The frosting should be spreadable but not too runny. Gently fold in the chopped pecans for that extra crunch.
Once the cake is baked and has cooled slightly, pour the frosting over the warm cake, spreading it evenly with a spatula. It’s okay if some of the frosting melts into the cake; that’s part of the charm.
For the final touch, melt 1/2 cup of butter in a small saucepan over low heat. Stir in cocoa powder and milk, mixing until well combined. Remove from heat and whisk in enough powdered sugar until smooth.
Pour this chocolate frosting over the top of the cake, spreading it out evenly with a spatula. Sprinkle the remaining chopped pecans on top for decoration. Allow the cake to cool completely before slicing and serving. Enjoy every bite of your delicious creation!
