In a large saucepan, melt butter over low heat. Add marshmallows and stir until smooth and melted. Remove from heat. Stir in the honey.
Stir in the cereal until well coated.
With a spatula, spread the mixture into the greased baking pan. Sprinkle with sea salt. Allow to cool completely. Cut into 2-inch squares. They're best if you serve them the same day!