Butter a 9×9-inch pan. In a large pot over medium-low heat, melt 3 tbsp butter, then add marshmallows and salt. Stir until smooth, 3 to 4 minutes.

Remove from heat and fold in the cereal and freeze-dried strawberries until evenly coated.

Press mixture into the prepared pan using buttered hands or parchment. Cool at least 30 minutes until set.

Turn out onto a board and slice into 16 squares. Serve or store.