Preheat the oven to 350°F.
Spray the bottom and sides of a 9x13x2-inch baking pan with cooking spray.
Prepare the marble cake batter as per the package directions and pour it into the pan.
In a large bowl, stir together the ricotta cheese, sugar, eggs, and vanilla extract until well combined and smooth.
Spoon the ricotta mixture evenly over the cake batter in the pan, making sure to go all the way to the edges of the pan.
Bake for 1 hour on the center rack of the oven or until a toothpick inserted in the center comes out clean. If your cake ends up with cracks in it (mine often does), that is fine. It will be covered up with the topping.
Place the pan on a wire rack and allow the cake to cool completely (this will take about 1½ to 2 hours).
In a medium bowl, mix together the chocolate pudding mix and milk until well-combined and smooth.
Add the Cool Whip to the pudding mixture and gently fold it in until it is well-combined.
Spread the pudding mixture evenly over the top of the cake.
Cover and refrigerate for at least 6 hours (overnight is even better).
Top the cake with chocolate sprinkles, if desired.
Slice into 12 pieces; serve cold.