Preheat the oven and prepare the Brussels sprouts - Preheat the oven to 425°F (220°C). Rinse the Brussels sprouts under cold water and pat them dry with a paper towel. Remove any wilted or yellow leaves, trim the ends, and slice off the bottom. Slice each Brussels sprout into thin rounds, discarding the tough stems. Place the sliced Brussels sprouts into a large mixing bowl. - For extra crispy Brussels sprouts, make sure to slice them as thinly as possible. Use a mandoline slicer if you have one, it's much easier and quicker than using a knife.

Coat the Brussels sprouts and roast them - Drizzle the Brussels sprouts with olive oil and season with salt and garlic powder. Toss everything to combine. Line a baking sheet with parchment paper (optional) and spread the Brussels sprouts in an even layer. Roast for 20-25 minutes, flipping halfway through cooking, until the slices are crispy and lightly charred. - Don't overcrowd the baking sheet, or the Brussels sprouts will steam instead of roast. Be sure to flip the slices halfway through cooking to ensure they cook evenly.

Make the spicy lime aioli - In a small mixing bowl, whisk together the sour cream, lime juice, adobo sauce, cumin, salt, and black pepper until smooth. Adjust the seasoning to taste, adding more salt or lime juice if needed. Set the aioli aside. - If the aioli is too thick, add a splash of water or milk to loosen it up. If you don't have adobo sauce, you can replace it with your favorite hot sauce for a similar kick.

Warm up the tortillas - Place the tortillas on a plate and microwave them for 20-30 seconds until they are warm and pliable. You can also heat them up in a dry skillet or on a gas flame for a charred flavor. - If you're using corn tortillas, they tend to crack easily, so it's essential to warm them up first to prevent that.

Assemble the tacos - To assemble the tacos, spread a generous amount of the spicy lime aioli on each tortilla. Top with the crispy Brussels sprouts, sliced radishes, green onions, and cilantro. Serve immediately with lime wedges. - Feel free to add your favorite toppings to these tacos! Avocado, salsa, or chopped tomatoes would all work well.