PASTRY CREAM: Make up to 24 hours in advance OR refrigerate at least 2 hours prior to use.
In a medium saucepan, heat the milk, heavy cream and vanilla bean to a boil over medium heat. Immediately turn off the heat and set aside to infuse for 10 to 15 minutes.
In a medium bowl, whisk the egg yolks and granulated sugar until light and fluffy. Add the cornstarch and whisk vigorously until no lumps remain. Temper the eggs by whisking in 1/4 cup of the hot milk mixture until incorporated. Whisk in the remaining hot milk slowly.
Pour the mixture back into the saucepan. Cook over medium-high heat, whisking constantly, until thickened and slowly boiling. Remove from the heat and stir in the butter. Let cool slightly. Press mixture through a fine mesh strainer to remove any curdled bits and remove husk of vanilla bean. Cover strained pastry cream with plastic wrap, and press the plastic wrap on top of the pastry cream to make sure it doesn’t form a skin. Chill at least 2 hours or until ready to serve.
CHOCOLATE GANACHE: In small saucepan, over medium heat, combine heavy cream and chocolate. Whisk until melted and the two are completely combined. Remove from heat; set aside to cool and thicken while preparing pancakes.
PANCAKES: In large bowl, whisk together pancake mix and cake mix. Stir in milk, two whole eggs and vanilla until the mixture is smooth. Heat a large griddle or skillet over medium-high heat. Spray with non-stick cooking spray. Pour 1/3 cup of batter into pan or griddle and allow to cook until golden brown on the bottom, 2-3 minutes. Flip pancake over and continue to cook until the other side has turned golden brown, about 1 1/2 minutes. Remove from griddle/skillet and allow to cool.
TO ASSEMBLE: Stack 2 to 3 pancakes, layer pastry cream between each pancake. Pour chocolate ganache over the top and promptly devour!