In a small saucepan or skillet, melt the butter over medium-low heat.
Add the brown sugar, cinnamon, salt, and pumpkin seeds. Stir to coat evenly.
Cook, stirring frequently, for 6–8 minutes, until the sugar is melted and the seeds are lightly browned and fragrant.
Immediately spread the mixture onto a parchment-lined baking sheet in an even layer.
Allow to cool completely — the coating will crisp as it cools. Sprinkle with a little flaky sea salt.
Once cooled, break apart any clusters and store in an airtight container.