Fold in the reserved un-melted marshmallows, before transferring into a pan. Using a buttered spatula, press firmly into a greased 13x9. pan. Melt semi-sweet chocolate in microwave in 30 second intervals, stirring in between, until fully melted. Carefully drizzle bars with melted chocolate. Sprinkle with salt. Cool completely. Cut into bars. Serve immediately or store in an airtight container.