Whisk together vanilla pudding mix and 1 cup milk for 2 minutes. Set aside.
With a mixer, beat together 1 cup heavy cream and ½ cup powdered sugar for 3 minutes. Fold mixture into pudding mix. Refrigerate.
Pour oil into a large skillet over medium heat. Fry each biscuit for 2-3 minutes on each side until golden brown. Allow to cool.
Stir together 2 tablespoons heavy cream, 2 tablespoons milk, butter, vanilla, and corn syrup in pan over medium. Once butter is melted, turn to simmer and add chocolate. Continue to stir until smooth.
Remove from heat and whisk in 2 and ¼ cups powdered sugar.
Fill pastry bag with creme and press tip into side of biscuit, filling donut with custard.
Dip tops of donuts into frosting.
Recipe by Rachel Schultz at https://rachelschultz.com/2014/08/14/boston-creme-donuts/