Preheat oven to 350*. Toss Brussels sprouts in 2 tablespoons vegetable oil (make sure they’re all coated lightly) and spread on a cookie sheet. Roast for 15-20 minutes, until crispy and slightly browned.
Whisk all the sauce ingredients together. Once the Brussels sprouts are done, toss them in the sauce and set aside.
Heat 1 tablespoon vegetable oil in a skillet and add the skiitakes. Sauté for 2-3 minutes, then stir in chile powder and juice of half the lime. Remove from heat and assemble tacos with Brussels sprouts, shiitakes, sliced avocado, black beans and remaining lime juice.