Black bean brownies (Toddlers and beyond)

Name: Black bean brownies (Toddlers and beyond)
Prep time: 15 min
Cook time: 25 h 20 min
Total time: 25 h 35 min
Cuisine: American
Ingredients: 170 g dried black beans (see Tips); 600 g filtered water, plus extra for soaking; 60 g virgin coconut oil, plus extra for greasing; 100 g dark chocolate (70% cocoa) (see Tips); 3 eggs; 30 g raw cacao powder (see Tips); 2 tsp natural vanilla extract; 80 g coconut sugar (see Tips); 1 tsp gluten free baking powder; 50 g walnuts (optional - omit for nut-free); raw cacao nibs, for sprinkling (optional)