Turn on the oven over 175 C (fan).
Remove dates seeds and cut into pieces or soak them first into hot water for 2 to 5 minutes (or until soft).
Meanwhile, in a medium bowl, mash the banana and mix it until smooth (it might be slightly chunky).
Add oats and dates pieces to the banana mixture. Using a wood spoon, mix them until well combined.
Finally, chop the nuts in a small blender or in a mortar. Add them to the mixing bowl and mix again. The mixture should bind to itself when pressed together.
Using parchment paper, line 3 small tart tins (12 cm or 5 inches diameter). Brush the parchment with a bit of coconut oil. Divide the mixture in 3. Press each dough into the tart tins and create a tart shell using your fingers.
Place in the oven and bake for 15 minutes (or until they become golden brown on the edge). The center should be cooked too but less than the edges. Let them cool down. Only, when they are at room temperature remove the parchment paper.