Preheat oven to 425 degrees F. Line a baking sheet with a silicone mat or parchment paper.
In a large mixing bowl, add the avocado oil, miso paste, and vinegar. Whisk until well combined. Add the halved Brussels sprouts and stir with a wooden spoon or spatula until all the Brussels are evenly coated with the miso mixture. (We don’t add the maple syrup until the end because it makes the Brussels sprouts burn faster.)
Place on the baking sheet, making sure the Brussels sprouts are not touching each other and most are facing cut side down (it’s okay if not all of them are). Also, make sure you don’t over crowd the pan. Bake for about 25-30 minutes. You want them basically charred looking, but not burnt.
Remove from pan and place back into the mixing bowl you were using. Add the maple syrup, sesame oil, and optional chili flakes. Stir until combined. Sprinkle some sesame seeds on top and enjoy!