Line two large baking sheets with parchment paper or silicone mats.
In a large microwave-safe bowl, melt milk chocolate chips in 20-30 second bursts, stirring between each until smooth.
Stir peanut butter into the melted chocolate until fully combined and smooth.
Add Rice Krispies and gently stir to coat evenly.
Let the mixture cool a few minutes, then stir in the marshmallows so they stay soft and don't melt.
Use a cookie scoop or spoon to drop clusters onto the prepared baking sheets.
Sprinkle with mini chocolate chips and sea salt (if using). Refrigerate for 45-60 minutes or until set.
