Create your flax eggs by mixing together the ground flaxseed and warmed cashewmilk (you can heat it up on the stovetop or in the microwave, whichever you prefer). Refrigerate for 15 minutes before adding into the batter.
Drain and rinse black beans, then put in a large mixing bowl with melted coconut oil, maple syrup, coconut sugar, and peppermint extract. Use an immersion stick blender (or a high speed blender will work) to puree the beans until smooth.
Add in all remaining ingredients, including flax eggs, and stir.
Use non-stick spray or additional coconut oil to grease the bottom of a 9 x 9 baking pan.
Pour in batter and bake for 30 minutes or until a knife comes out clean. The top edges of the brownies should start to come away from the pan.
Allow to cool for at least 30 minutes before slicing.