Line an 8x8-inch baking pan with parchment paper and lightly grease it.

Place Oreos in a zip-top bag and crush them with a rolling pin into large chunks. Set aside.

In a large pot, melt the salted butter over medium-low heat.

Reduce heat to low. Add the 10 oz bag of marshmallows (save the extra 1 cup for later) and stir constantly until completely smooth. Remove from heat immediately.

Stir in the vanilla extract and salt.

Gently fold in the crispy rice cereal until mostly coated in marshmallow.

Add the crushed Oreos and the reserved 1 cup of whole mini marshmallows. Fold gently just until combined.

Transfer the mixture to the prepared pan. Using greased hands, very gently press it into an even layer without packing it down tightly.

Allow to cool at room temperature for at least 1 hour before lifting out of the pan and slicing into thick squares.