Preheat your oven to 350. Lightly grease and flour a 10 inch Bundt cake pan.
In a large mixing bowl, prepare your cake mix according to the directions on the box and set that bowl aside.
In a separate large bowl, prepare the cream cheese filling. Mix together the egg, butter, cream cheese and vanilla extract.
Once that mixture is combined, turn the speed of your mixer down and slowly add the powdered sugar in.
Gradually increase the speed until the powdered sugar is incorporated. Continue mixing the filling until all of the ingredients are thoroughly combined, about two minutes.
Next, pour half of the cake batter into the Bundt cake pan. Then carefully add the cream cheese filling to the top of the cake batter.
Make sure to leave a 1-inch border around the pan. Then finish off the cake with the remaining cake batter.
Carefully use a serrated knife (like a butter knife) and lightly swirl the filling into the cake. ***Only swirl the knife a few times.
Bake the cake for 50 minutes. Start doing the toothpick test at five minute intervals until the toothpick comes out clean.
When the cake is done, pull the cake pan out of the oven and let it rest until the cake is completely cool. Once it’s completely cool, invert the cake onto the platter that you choose.
As the cake is cooling, you can prepare the frosting. Mix together the vanilla extract, milk, cream cheese and powdered sugar. Remember to SLOWLY add the powdered sugar! Mix the frosting together for about two minutes.
Pour the frosting into the squeezable disposable bottle and put the lid back on. Decorate the cake however you choose.
Slice the cake and enjoy!
Make sure to store the remaining cake in the refrigerator.