I recommend measuring the ingredients in grams using a kitchen scale. You can watch the video for visual instructions.
Rinse the dried red lentils thoroughly until the water runs clear. Place them in a bowl, cover them generously with water, and soak for at least 2 hours or longer.
Drain the soaked lentils very thoroughly. Their weight should be approximately 180 g after soaking.
Preheat the oven to 360 °F (180 °C).
Add the drained lentils, canned coconut milk, maple syrup, vanilla extract, apple cider vinegar, and banana to a high-speed blender. Blend until the mixture is completely smooth and creamy, stopping to scrape down the sides when necessary.
Add the ground almonds, cocoa powder, baking powder, baking soda, cinnamon, and salt. Blend briefly until a smooth, homogeneous brownie batter forms.
Pour the batter into a silicone brownie mold. My mold measures 8 x 4-inch (20 x 10 cm). Alternatively, use a loaf pan lined with parchment paper.
Break or chop the dark chocolate into small pieces and scatter them evenly over the batter.
Bake for approximately 28–30 minutes.
Allow the brownies to cool completely before carefully removing them from the mold and slicing them.