Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch baking dish.

In a mixing bowl, combine flour, sugar, cocoa powder, baking powder, and salt.

In another bowl, whisk together milk, oil, eggs, and vanilla extract.

Add the wet ingredients to the dry ingredients and mix until just combined.

Pour the batter into the prepared baking dish and bake for 30 minutes or until a toothpick comes out clean.

In a bowl, whisk together sweetened condensed milk, evaporated milk, and whole milk.

Once the cake is done, let it cool for 10 minutes, then poke holes all over the top with a fork.

Pour the milk mixture over the cake, allowing it to soak in.

In a mixing bowl, beat the heavy cream and powdered sugar until stiff peaks form.

Spread the whipped cream over the soaked cake and dust with cocoa powder.

Chill the cake in the refrigerator for at least 2 hours before serving.

Slice and enjoy your Chocolate Tres Leches Cake!