Preheat oven to 350ºF and line an 8x8-inch baking pan with two crossing sheets of parchment paper, leaving a few inches of overhang on the sides to allow for easy removal. Lighting grease the parchment with just a little coconut oil.
Add coconut oil and chocolate to a small bowl over a saucepan or in a double boiler set over low heat. Or in 30 second increments in the microwave. Stir frequently until the coconut oil and chocolate have melted, remove from the heat and setting aside to cool slightly.
Using a handheld mixer or a stand mixer fitted with the whisk attachment, beat together eggs, coconut sugar, and vanilla extract until smooth and pale, about 2 minutes. Add melted chocolate mixture and mix until well combined. Reduce speed to low and add cacao powder, arrowroot powder, Vital Proteins Collagen Beauty Greens, and salt, mixing until well combined, scraping down the sides of the bowl as necessary. Batter should be thick and smooth.
Pour batter into prepared pan, spreading it evenly with a greased spatula. Bake for 25-30 minutes, until the center is set. Remove from oven and let cool in pan for about 15 minutes before removing and transferring to a wire rack to cool completely. Cut into squares, sprinkle with large flaked sea salt, if you'd like and serve.
Notes
the Beauty Greens can be replaced with regular collagen peptides or you can also experiment with using other protein powders, which I have not done, myself.