Line a 9" square pan with foil and lighly coat with cooking spray.
In a large saucepan, melt the butter over medium heat. Add the marshmallows and stir until completely melted.
3 Tbsp butter, 3 cups (142g) mini marshmallows
Add in the rice cereal and mix until all the cereal is coated with the marshmallow mixture.
4 cups (125g) Rice Krispies cereal
Spoon onto the prepared pan and press into an even layer. Place in the fridge to cool while preparing the cheesecake layer.
Combine the gelatin and 3 tablespoons of water in a small microwave-safe bowl. Set aside to soften.
1 Tbsp envelope gelatin powder
Using an electric mixer, beat the cream cheese and powdered sugar together.
16 oz (2 packages/250 each) cream cheese, 1 cup (120g) powdered sugar
Mix in the sour cream and vanilla.
1 cup (255g) sour cream, 1/2 tsp vanilla extract
Microwave the gelatin for about 15-30 seconds to melt. Add the gelatin solution to the cream cheese mixture and blend until smooth. Pour over the rice cereal layer and smooth out the surface.
Loosely cover with plastic wrap or foil and chill for minimum of 2 hours or overnight. Cut into 16 squares and top with berries before serving.