Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a mixing bowl, combine ricotta cheese, sugar, and vanilla extract, then beat until smooth. Add eggs one at a time, mixing well.

Prepare the chocolate cake mix according to package instructions, combining with canola oil, water, and eggs until smooth.

Pour the chocolate cake batter into the greased baking dish and spread evenly. Spoon the ricotta mixture over the cake batter without stirring.

Bake for 1 hour to 1 hour and 10 minutes until set but slightly jiggly in the center.

Allow the cake to cool completely in the baking dish for about 1 hour.

Mix the instant chocolate pudding with cold milk, whisk until smooth, then fold in whipped topping.

Spread the chocolate pudding frosting evenly over the cooled cake and refrigerate for at least 4 hours or overnight.