Preheat the oven to 375 degrees.
Chop the cashews and almonds quite fine in a food processor. Mix with 1 cup almond flour, oatmeal, baking powder, and salt.
Stir well, then pour in 3/4 cup coconut oil over it and add 2 Tablespoons honey.
Mix this with clean hands so it stays crumbly. If it's too dry, add a little more coconut oil.
In 9x13 baking pan, greased with a thin layer of coconut oil, spread 3/4 of your crumble evenly over the bottom and press down firmly.
Put the pan in the oven and bake for about 10-12 minutes, or until the top begins to brown.
In the meantime cut the plums cut into pieces. Put the plums in a bowl and mix with 2 Tablespoons honey, 2 Tablespoons almond flour, 2 Tablespoons coconut oil, and cinnamon.
Remove the baking pan from the oven once browned and spread the plum mixture evenly over the bottom.
Sprinkle the crumble that you have left over the top of the plums.
Put the pan back in the oven and bake for 35-40 minutes until the top is nicely browned.
If the top starts to brown too soon, you can cover the pan with aluminum foil.
Then remove from the oven and let cool completely. Then place pan in the refrigerator for a few hours to set completely before cutting into bars.
Using a sharp knife, divide into 16 bars and store in an airtight container in the refrigerator. Or freeze half for later.