Combine dates and coconut oil in a small bowl and let soak for 30 minutes.
Transfer to blender and add cacao powder, 1/2 cup agave and process until very smooth. (This is a bit tricky and will require some patience. I have not yet discovered the trick to completely processing the dates. Sometimes it helps to chop the them in the small pieces. If you have a high powder blender this should not be an issue.).
In a separate bowl, combine peanut butter, vanilla and 2 tbsp agave and mix well.
Place 12 foil mini muffin cups on a large plate. Fill each cup about halfway full with the chocolate mixture. Gently spread about 1 teaspoon peanut butter in each cup. If you have more peanut butter left over after you have filled each cup, you can add more or just eat it plain! ;).
Top the cups with the remaining chocolate, covering the peanut butter completely.
Chill the cups in the fridge for about 2 hours before serving. They will keep for about 5 days in the fridge.