Boston Cream Poke Cake

1 box yellow cake mix (plus box ingredients)
2 boxes instant vanilla pudding mix
4 cups milk
1 container chocolate frosting

Prepare cake in 13 x 9″ pan according to box directions. Use spoon handle to poke holes evenly across cake. Combine milk and pudding mix and whisk until well blended. Pour pudding over cake making sure it gets down into holes. Refrigerate cake for several hours to allow pudding to settle and set up. Open frosting container and remove foil seal. Microwave for 15 seconds and stir. Repeat this until frosting is pourable. Pour over pudding layer and spread with spatula to cover completely. Refrigerate for at least several more hours.