Soak dates in warm water for 10 minutes, then drain.
Add pistachios to a blender and blend for 3-5 minutes, scraping down the sides as needed, until a smooth butter forms. Set aside.
Add rolled oats and drained dates to a food processor. Blend until a sticky dough forms.
Scoop 1 Tbsp oat mixture into each cup of a silicone muffin tray. Press down firmly with your fingers until you have a flat, even base layer.
Add 1 Tsp pistachio butter to each cup and smooth into an even layer.
Melt the chocolate in a microwave in 10-second increments, stirring thoroughly between each interval, until fully melted.
Spoon 1 Tsp. melted chocolate over each cup and smooth into an even layer.
Finish each cup with a pinch of flaky sea salt.
Transfer to the freezer for 30 minutes or the fridge for 1 hour, until the chocolate is fully set.
Pop the cups out of the silicone tray and serve. Store leftovers in the fridge.