Soak the cashews. Add the cashews to a medium bowl, cover them with water, and let them soak for at least 8 hours to soften up and blend easily. You can also add 1tsp./5.7 g of salt to the soaking water to help activate the cashews and neutralize enzyme inhibitors in the nuts. Once soaked, drain the soaking water and rinse the cashews.
Blend the cashews and maple syrup. Add the soaked cashews and maple syrup to a high-speed blender or a food processor bowl fitted with an S blade and blend until smooth. You'll end up with a thick, sticky paste, which will serve as a binder in these brownies. If you don't have a high-speed blender or a food processor, use cashew butter instead of whole cashews.
Mix in the rest of the brownie ingredients. If you're using a blender, transfer the cashew mixture to a medium bowl, and using a spatula, fold in the almond flour and cocoa powder. If you're using a food processor, add the almond flour and cocoa powder to the food processor and process until well combined. The mixture will be very thick, almost dough-like.
Press the mixture into a pan. Transfer the mixture to a parchment paper-lined baking dish (I used a 5.5 x 7.5 inch/14 x 19 cm glass container) and press it into a smooth, even layer.
Mix the chocolate ingredients. Add the coconut oil, cocoa powder, and maple syrup to a medium bowl and whisk until smooth.
Assemble the brownies. Pour the chocolate on top of the brownies and spread it evenly. Tap out any air bubbles.
Chill. Transfer the brownies to the refrigerator to firm up, for about 1 hour. Once firm to the touch, remove the brownies from the baking dish (by lifting the parchment paper) and cut them into squares. To cut the brownies cleanly, run a sharp knife under hot water for about 20 seconds, wipe off excess water, and press the knife down slowly, making the first cut. Run the knife under hot water again to reheat it. Wipe the blade clean, then make the second cut. Repeat until all the brownies are cut.
Store. Leftover brownies keep well in an airtight container in the refrigerator for up to 2 weeks. For longer-term storage, freeze in an airtight container for up to 3 months. The freezer will produce condensation on the chocolate if the brownies are brought to room temperature straight from the freezer. So, for best results, transfer the frozen brownies to the refrigerator 24 hours before serving.