Place dates in a small bowl covered with water. Microwave for 30 seconds then drain.
Spoon mixture out onto a parchment-lined plate. Smooth and spread mixture with a rubber spatula until 1/2-inch thick. Sprinkle with pistachios and a generous amount of flaked sea salt.
Transfer to freezer and freeze for 2 hours until very firm.
Melt remaining 1 tablespoon coconut oil in microwave. Stir in cacao powder. Drizzle over the fudge and watch it harden within a minute. Slice fudge into desired pieces. Store in freezer and let rest on countertop 10 minutes before serving. Fudge will be too soft if stored in fridge.