Stir melted butter in with crushed Oreos and press 1 teaspoon crumbs into the bottoms of dessert shooter cups. Pour peanut butter mixture into a plastic baggie, snip the corner, and pipe into the cups (on top of the crumbs). Sprinkle the tops with another ½ teaspoon of crumbs. Top with a sprinkle of sea salt for an extra sweet-salty combo. Refrigerate until ready to serve.