Melt the butter and cream cheese in a large pot over medium heat. Then add in the marshmallows and let them melt completely, stirring, then add the Rice Krispies, sea salt, and cinnamon. Mix it all together.
Pour into a 9-by-13-inch pan, being careful not to pack it in. If you press down on the Rice Krispies, they’ll get hard and crunchy.
Let them cool to room temp and then cut up.