Preheat the oven to 350 F (177 C). Lightly grease the bottom and sides of a 9 x 13 inch cake pan.
In a large mixing bowl, whisk the oil, eggs, milk, pumpkin puree, spices and cake mix until well combined. Pour the spiced pumpkin cake into the prepared cake pan.
½ cup (120 ml) vegetable oil, ½ cup (120 ml) water or milk, 4 large eggs, room temperature, 15 oz. canned pumpkin puree, 1 - 2 teaspoons pumpkin spice, 15.25 oz. spiced or yellow cake mix
Bake for 28 - 35 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Cool the cake in the cake pan to warm room temperature. Once the cake has cooled for 1 hour or is no longer very warm to the touch, poke holes in the cake using the bottom of a thick skewer or small wooden spoon. In another large bowl whisk the evaporated milk, condensed milk and heavy cream or half and half until smooth and well combined. Pour the three milk mixture on top of the cooled cake. The milk should soak into the cake easily. Cover the cake and pan with plastic wrap and transfer to the fridge to soak and chill overnight or for at least 4 - 6 hours. The longer the cake soaks, the better. 12 oz. evaporated milk, 14 oz. condensed milk, ¾ cup (180 ml) half and half or heavy cream
When you are ready to serve the pumpkin tres leches cake, make the spiced whipped cream. Add the heavy cream, sugar and vanilla extract to a mixing bowl fitted with a whisk attachment. Combine the ingredients on low for 1 minute. Increase the speed of the mixer to medium speed. Mix for about 4 - 5 more minutes or until the cream has whipped to medium stiff peaks.
2 cups (480 ml) cold heavy cream, 2 tablespoons (25 g) sugar or maple syrup, ½ teaspoon vanilla extract
Top the pumpkin milk cake with the whipped cream and a light dusting of cinnamon and enjoy.
1 teaspoon ground cinnamon