For super thick Rice Krispie Treats, grease an 9x9-inch baking pan with nonstick cooking spray. For regular Rice Krispie Treats, grease a 9x13-inch baking pan with nonstick cooking spray. You can also line the pan with parchment paper to make it easier for them to come out of the pan. Set pan aside.

In a large pot, melt the butter over medium high heat. Add the 16 oz bag of marshmallows and stir until the marshmallows are completely melted.

Remove the pan from the heat and stir in the vanilla extract and salt. Add the Rice Krispies and chopped Oreo cookies; gently stir until well coated with the marshmallows. Stir in the remaining 2 cups of mini marshmallows and white chocolate chips.

Transfer mixture to the prepared pan. Lightly press the mixture into the pan, using a greased spatula. You can also lightly grease your hands and press the mixture into the pan.

For the topping, place white chocolate chips and oil in a small bowl. Heat in microwave in 30 second intervals, stirring in between, until melted and smooth.

Drizzle the white chocolate over the Rice Krispie Treats. Top with chopped Oreo cookies.

Let the Rice Krispie Treats sit until chocolate is hard, about 1 hour. Cut into squares and serve.

Cover pan with plastic wrap or put the treats in an airtight container and store on the counter for up to 3 days.