In a medium bowl, whisk the vanilla pudding, milk, and sour cream until smooth and fully incorporated (you can also use a hand mixer to do this). Set aside and let it thicken.
To a 9x13 inch pan, add half of the cubed angel food cake, followed by 2 thirds of the blueberry pie filling on top of the cake, and then layer the remaining angel food cake over it.
Spread all of the vanilla pudding mixture on top of the cake layer followed by whipped topping. Smooth out the top with a spatula.
Drop spoonfuls of the remaining blueberry pie filling on top of the whipped topping, and swirl it with a butter knife. Chill the dessert in the fridge for at least 4 hours, or overnight. Before serving, sprinkle with slivered almonds.
Notes
Use a Serrated Knife: The easiest way to slice a fluffy angel food cake without squishing it, is with a serrated knife using the sawing motion.
Chill: It is important to allow the cake to set in the fridge for at least 4 hours before serving. You certainly can eat it after you layer it, but it won't taste as good.
Turn this cake into a trifle! Layer in a trifle bowl instead of a 9x13 pan. You can also make individual cups or even use mason jars if you like.
Substitutions: You can change up the flavor of the instant pudding to french vanilla, cheesecake, strawberry, lemon, or even chocolate. As for the pie filling, use strawberry, cherry, or apple. You can also use a different type of cake, yellow cake will be less fluffy and airy but it will still be delicious. If you'd rather not use whipped topping, substitute it with 1 cup of homemade whipped cream with a couple of tablespoons of powdered sugar.