Line an 8-inch square baking dish with parchment paper.

In a small saucepan, bring 1/2 cup of water, sugar, and corn syrup to a boil. Attach a candy thermometer and cook until mixture reaches 240°F.

Meanwhile, in a mixing bowl, sprinkle gelatin over the remaining 1/2 cup water and let bloom.

Once the syrup reaches 240°F, carefully pour it into the gelatin mixture while the mixer is at medium speed. Mix until well combined and fluffy, about 5 minutes.

Add vanilla, salt, and melted butter to the marshmallow mixture and beat until smooth.

Stir in Rice Krispy cereal, crumbled Oreos (reserve some for topping), and mini marshmallows until evenly coated.

Transfer the mixture to the prepared baking dish. Press down gently and sprinkle remaining Oreos on top. Use a spatula or your hands to level the surface.

Refrigerate for 10-15 minutes until set. Slice into bars and serve.