Line a 9×13 pan with parchment paper, lightly mist with nonstick cooking spray, and set it aside.
In a large pot, melt 1 cup of unsalted butter. Stir continuously until the butter just starts to brown. Remove it from heat immediately to prevent burning.
Quickly stir in the vanilla extract; the mixture will bubble up, so keep stirring for an additional thirty seconds until the sizzling subsides. Add salt.
Mix in half of the marshmallows and stir until almost completely melted before adding the remaining marshmallows. Stir until all marshmallows are entirely melted.
Add the Rice Krispies 2 cups at a time, lightly stirring until combined. Continue until all the Rice Krispies are evenly mixed. Fold in 2 cups of roughly chopped Oreos using a spatula.
Pour the mixture into the prepared 9×13 pan. Lightly wet your hands and gently press the mixture into the pan without crushing it.