Preheat oven to 325F (160C). Line two baking or cookie sheets with parchment paper or spray lightly with oil.
Put the almonds in a food processor and pulse several times until they are small chunks but not completely ground (see pic below). Dump the almonds in a medium bowl and set aside.
Add the oats to the food processor next and pulse just a few times as well until they are slightly broken down, then dump them into the bowl with the almonds.
Add the flour, baking soda, cinnamon and salt to the almonds and oats and mix well.
Rinse out the food processor, then add the prunes and hot water. Puree them together till mostly smooth.
Add the peanut butter and maple syrup to the processor with the prunes and puree all together.
Add the prune mixture to the oats mixture and stir until all combined to form a cohesive dough. You may need to use your hands to get it to come altogether (the dough is great raw – try it, but don’t forget to save some for cookies!).
Roll the dough out between two pieces of wax or parchment paper to about 1/2 inch (1 cm) thickness and then cut out rounds. I used a 3 inch (7 cm) cookie cutter but you can make them any size, just be sure to adjust your baking time.
Place cookies on prepared baking sheet 1 inch (2.5 cm) apart and bake for 8-10 minutes, until bottoms are lightly browned.
Remove from oven and move to a wire cookie rack to cool.
When cookies are completely cooled, spread the ganache onto them and sandwich together. If the ganache is hard to spread, let it sit at room temp for 10 minutes and it will soften.
Cookies can be kept in an airtight container at room temperature up to 5 days, or in the refrigerator up to 7 days. They can also be individually covered in plastic wrap and frozen for up to 3 months. Just let them thaw 5-10 minutes before eating.