Follow these detailed steps to assemble your Boston Cream Poke Cake. We’ll break it down into four main parts: baking the cake, preparing the filling, assembling the poke cake, and creating the ganache topping for a flawless result.

Part 1: Baking the Cake

1. Preheat and Prepare: Begin by preheating your oven to 350°F (175°C). Generously grease and flour a 9×13-inch baking pan. This step is crucial to prevent the cake from sticking, ensuring you can serve clean, beautiful slices later on. Alternatively, you can spray the pan thoroughly with a baking spray that contains flour.
2. Mix the Cake Batter: In a large mixing bowl, combine the yellow cake mix, water, oil, and eggs as directed on the box. Using an electric hand mixer or a stand mixer, beat on low speed for about 30 seconds to combine the ingredients. Then, increase the speed to medium and beat for 2 minutes. This process aerates the batter, which leads to a lighter, fluffier cake. Be careful not to overmix, as this can develop the gluten too much and result in a dense cake.
3. Bake to Perfection: Pour the prepared batter into your greased 9×13-inch pan, using a spatula to spread it evenly into the corners. Place the pan on the center rack of your preheated oven. Bake for 28-33 minutes, or until a wooden toothpick or cake tester inserted into the center of the cake comes out clean with a few moist crumbs attached, but no wet batter.
4. Cool Slightly: Once baked, remove the cake from the oven and place it on a wire cooling rack. Let the cake cool in the pan for about 15-20 minutes. It’s important that the cake is still warm when you poke the holes, as this helps the pudding absorb more effectively.

Part 2: Preparing the Pudding Filling

1. Whisk the Pudding: While the cake is cooling, prepare the vanilla pudding filling. In a medium-sized bowl, pour the two packets of instant vanilla pudding mix. Slowly pour in the 4 cups of cold milk while whisking continuously.
2. Combine Until Smooth: Continue to whisk for about 2 minutes. The mixture will start to thicken into a smooth, creamy pudding. It’s important to ensure there are no lumps. The pudding should be thick but still easily pourable. Setting it aside for a moment will allow it to thicken slightly more before you pour it over the cake.

Part 3: Assembling the Poke Cake

1. Poke the Holes: Take your warm cake (still in the pan) and use the round handle of a wooden spoon or a similar utensil to poke holes all over the top surface. Space the holes about 1 to 1.5 inches apart. Poke all the way down to the bottom of the cake, but be gentle to avoid tearing it. These holes are the channels that will carry the delicious pudding filling throughout the entire cake.
2. Pour the Pudding: Immediately after poking the holes, slowly and evenly pour the prepared vanilla pudding over the entire surface of the warm cake. Use a spatula to gently spread the pudding, making sure it covers the cake from edge to edge and seeps down into the holes you created. It might look like a lot of pudding, but trust the process—the cake will absorb it beautifully.
3. Chill the Cake: Cover the pan with plastic wrap or a lid and place it in the refrigerator. Let the cake chill for at least 3 hours. This chilling time is absolutely essential. It allows the pudding to fully set and the cake to absorb the moisture, resulting in an incredibly moist and flavorful dessert. Chilling overnight is even better for the best flavor and texture.

Part 4: Making the Chocolate Ganache Topping

1. Heat the Cream: Just before you’re ready to serve the cake, make the chocolate ganache. You can do this using a microwave or a stovetop.
   • Microwave Method: Pour the heavy whipping cream into a microwave-safe bowl. Microwave on high for 60-90 seconds, or until it is hot and steaming with small bubbles forming around the edges. Do not let it boil over.
   • Stovetop Method: Pour the heavy cream into a small saucepan and heat it over medium heat until it begins to simmer around the edges.
2. Melt the Chocolate: Remove the hot cream from the heat source. Immediately add the semi-sweet chocolate chips to the hot cream. Let the mixture sit undisturbed for 5 minutes. This allows the heat from the cream to gently and evenly melt the chocolate chips, which prevents the chocolate from seizing or burning.
3. Whisk Until Smooth: After 5 minutes, begin to whisk the mixture. Start from the center and work your way out in small circles. The ganache will come together, transforming into a glossy, smooth, and rich chocolate sauce. Continue whisking until it is completely smooth and uniform in color.
4. Top the Cake: Remove the chilled cake from the refrigerator. Pour the warm chocolate ganache over the top of the set pudding layer. Use an offset spatula or the back of a spoon to spread the ganache evenly over the entire surface.
5. Final Chill: Place the cake back in the refrigerator for another 30 minutes to an hour. This allows the ganache to set slightly, making it easier to slice and serve. Once the ganache is set, your Simple Boston Cream Poke Cake is ready to be enjoyed!