Brown the butter

• Melt the butter in a saucepan over medium heat.
• Keep cooking until it turns golden brown and smells nutty.

Melt the marshmallows

• Lower the heat and add the mini marshmallows.
• Stir until completely melted and smooth.
• Stir in the vanilla, salt flakes and condensed milk.

Combine with the cereal

• Remove from the heat and fold in the Rice Krispies cereal until evenly coated.
• Fold in the chopped Oreos.

Press into the dish

• Transfer the mixture to a lined baking dish and press it down evenly.
• Scatter the mini marshmallows and sprinkles over the top.

Cool and serve

• Let the treats set at room temperature before slicing.