Line an 8×8-inch baking dish with parchment paper, ensuring that the paper extends beyond the sides to facilitate easy removal once the fudge has set.

In a large saucepan, combine the granulated sugar, unsalted butter, and heavy cream. Bring the mixture to a gentle boil over medium heat.

Reduce the heat to medium-low and continue cooking for 7 minutes, stirring continuously to prevent scorching. To confirm readiness, drop a small amount of the mixture into a glass of ice water. It should form a soft, fudge-like ball.

Remove the saucepan from the heat. Immediately add the white chocolate chips and stir until fully melted and smooth.

Add the marshmallow creme and blend thoroughly until the mixture is uniform.

Whisk in the vanilla instant pudding mix and vanilla extract until fully incorporated.

Pour approximately two-thirds of this mixture into the prepared baking dish, spreading evenly.

Add the unsweetened cocoa powder to the remaining portion of the fudge mixture and stir until well combined.

Pour this chocolate mixture over the first layer and use a knife or skewer to create a gentle swirl pattern.

Allow the fudge to cool completely at room temperature. Once fully set, remove it from the pan using the parchment overhang and cut it into squares of the desired size.

In a microwave-safe bowl, combine the semisweet chocolate chips and vegetable oil. Heat in 30-second intervals, stirring between each session, until the mixture is smooth and fully melted.

Allow the melted chocolate to cool for approximately 15 minutes. Dip the top of each fudge square into the chocolate topping.

Place the dipped pieces on parchment paper, chocolate-side up, and allow them to set for roughly 1 hour.