Preheat the oven to 350° F (176 °C).

In a bowl, add the flour, almond flour, baking soda, and salt and press and mix well to break any of the almond flour lumps. Make a well in the center of the dry ingredients.

Add in the flax egg and 3 tablespoons of maple syrup and mix until it starts to form somewhat of a dough. If the dough is too crumbly, add in more maple syrup.

Line and 8x8- or 9x9-inch baking dish or a brownie pan with parchment, then press this crust into the pan and even it out with the spatula. Use a fork to make holes in the crust, and then bake for 18 to 22 minutes or until golden on the edges.

Once the crust is done baking, remove it from the oven, and let it cool.

Add the cashews, mango puree, salt, and sugar to a blender, and then blend for a minute. Then leave the blender and let it sit for 5 to 10 minutes for the blended cashews to rehydrate from the moisture in the mango puree. Then blend again for a minute and let it sit for another minute and blend again for half a minute. Repeat this until the mixture is super creamy. Taste to adjust sweetness and flavor. You can add a little bit of vanilla, if you like.

Pour or scoop this mixture, depending on how thick it is, over the baked and cooled crust, and even out the top with a spatula. Then, put the baking dish in the freezer for an hour or two, until the bars are somewhat set, and then you can slice them and serve them.