1. In a bowl, mash the bananas until they become a puree.
2. Add the rest of the ingredients, except the buckwheat, and mix well.
3. Refrigerate for at least 1 hour.
4. Form small balls and flatten them, transfer them to a baking sheet (with parchment paper).
5. Bake for 15 minutes at 180ºC/350°F.
6. Remove the cookies and let them cool at room temperature.
7. Melt the chocolate with a little coconut oil, and pour it over the cookies.