Line a muffin pan with 9 muffin liners. Pre-heat the oven to 375°.
In a large bowl, combine the flour, flax seeds, cacao powder, baking powder and salt.
In a medium bowl, combine the mashed avocado, maple syrup, vanilla extract and milk. Stir to combine.
Transfer the avocado-milk mixture to the dry ingredients and stir to combine. Make sure there are no dry pockets left (use a spatula if you need), but try not to overmix as well. Then, add the shredded beets and chocolate chips and stir until combined.
Transfer the batter equally in between the prepared 9 muffin tins and cook in the oven for 18 minutes. I like to use a ice cream scoop as the dough is sticky.
Once cooked, let them cool down in the muffin pan for about 10 minutes before eating. Enjoy!