Boston Cream Poke Cake

Make the Cake
24 You'll need the cake mix and whatever other ingredients called for on the cake mix box. This varies from brand to brand so I didn't include them here.
2 Make the cake according to directions on the box, baking it in a 13x9-inch pan.
3 While the cake is still warm poke holes all over the cake at about 1 inch intervals using a dowel or glass straw about the same diameter as a pencil - maybe a little bigger.
4 Poke through the cake to the bottom but not thru the bottom.
Prepare the Pudding
7 Whisk pudding mix with 3 1/2 cups of whole milk. OR make the homemade pudding according to instructions. Do not let it set up or it will be too thick to go into the holes in the cake.
8 Pour evenly over the cake getting it into all the holes. A lipped measuring cup works great for this.
9 Spread the pudding over the cake pushing it gently into the holes.
10 Add the remaining pudding for a thick layer on the top of cake.
11 Chill for at least 2 hours or overnight.
Make the Ganache
14 Heat the cream in the microwave until almost bubbling.
15 Remove from the microwave and stir in the chocolate until it's melted and completely smooth.
16 Stir in the butter and the corn syrup.
17 Pour over chilled cake and smooth with a spatula.
18 Return to the refrigerator for 2 hours or more.
To Use Canned Frosting (Instead of Homemade Ganache)
21 Open a container of chocolate fudge frosting and microwave in 10 second intervals. Stir between each interval until the frosting is pourable.
22 Don't overheat the frosting and watch it very carefully. If it get's too hot it will separate and be runny. You won't be able to use it. 
23 Pour chocolate frosting over the cake and refrigerate as directed in the recipe.