Preheat oven to 350°F (180°C) and grease or line a 9x13 inches (22 x 32cm) rectangular cake pan.
In a large mixing bowl, combine the white cake mix, buttermilk, vegetable oil and eggs. Mix using an electric mixer until just about combined.
Divide batter evenly between three smaller bowls. Add a few drops of food colouring into each bowl, then mix with a spatula or whisk to combine.
Using three large spoons, add spoonfuls of each colourful batter into the greased cake pan.Alternate each colour to create a marbled effect. Once all the batter has been added, use a long skewer or tip of a knife to gently swirl the colours. Do not combine them too much, a slight marbled effect is enough.
Bake for 25 minutes or until a skewer comes out clean.
Using the end of a wooden spoon, poke multiple holes into the hot cake about 1 ½ inch apart from each other.
Let the cake cooldown for 10-15 minutes. In the meantime, prepare the filling as indicated on the packaging. It needs to be runny, so don’t allow it to set before using.
Pour the vanilla pudding or custard over the cake, ensuring all the holes are filled. Tap the baking pan on the work surface a few times to force the pudding to seep into the cake. Spread the remaining pudding on top of the cake.
Chill for 30-40 minutes or until completely cold before frosting.
Start whipping the cream and vanilla extract until soft peaks, then gradually add in the powdered sugar. Continue whipping until medium-stiff peaks.
Spread the whipped cream or Cool Whip on top of the cold cake, levelling it with a spatula.
Decorate with sprinkles, Easter eggs or chocolate carrots. Enjoy.
Notes
I recommend using a kitchen scale in grams for more accuracy. The cups used for the conversion are standard US customary cups (1 cup flour = 136g). There are many different types of cups across the globe, which is why I strongly recommend using grams instead.
Nutritional information is indicative only and is calculated per slice (this cake yields 16 slices).
Buttermilk can be replaced with sour cream, Greek yogurt or heavy cream.
Vegetable oil - use either sunflower or canola oil.
Vanilla pudding - liquid quantity might differ depending on the brand you buy. Please follow packaging instructions.
Cool Whip can also be used instead of whipping cream.
Vanilla extract can be replaced with vanilla bean paste.
Nutrition
Calories: 320kcal
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