Line an 8x8 square pan with parchment paper, leaving overhang on the sides.

In a large saucepan or Dutch oven, add butter. Turn heat to medium and let the butter melt. As the butter begins the browning process, it will start to sputter and foam. Continue stirring with a nonstick spatula to ensure even heat. It will take anywhere from 5-9 minutes for the butter to go from golden brown to a deeper brown. Normally, we would wait for the butter to fully brown, but in this case it will keep cooking with the marshmallows, so when it turns golden brown, add the full bag of mini marshmallows.

Turn the heat to LOW. Let the marshmallows and butter cook until they are completely melted and run off the spatula.

Add in the Rice Krispies, salt, and cinnamon. Mix to combine. Remove from heat and add in the remaining half bag of mini marshmallows. Mix again to distribute.

Scoop half of the mixture into the prepared pan and press down lightly with a greased nonstick spatula.

Dollop the dulce de leche on top of the Rice Krispies layer and spread with an offset spatula.

Place the remaining half of the mixture on top of the dulce de leche layer and press down slightly (don't pack it down too much or it won't be as gooey!).