Prepare the corn (if using fresh corn on the cob): Char the ears of corn in a cast-iron skillet over medium-high heat for about 15 minutes, rotating every 5 minutes, or until there's an even char on all sides. Once cool enough to handle, slice off the kernels.
Make the maple chipotle glaze: Sauté diced shallot and garlic in a little olive oil over medium heat for about 2-3 minutes. To a blender, add chipotles, Adobo sauce, vinegar, maple syrup, sautéed shallot and garlic, and spices and blend until creamy.
Prepare the Brussels sprouts: Preheat the oven to 400°F. Wash, de-stem, and slice Brussels in half lengthwise (or into quarters if large). Heat a large cast-iron skillet over medium-high heat and then add oil. Once the oil is hot, add Brussels sprouts, cut-side down in a single layer, and cook for about 3-4 minutes, or until they develop a nice caramelization. Toss quickly and transfer to the oven for another 5-10 minutes, or until perfectly tender. Remove from the oven, pour in the maple chipotle sauce, and toss to coat.
Load grilled tortillas with Brussels sprouts, beans, charred corn, lemon crema, and pickled red onions. If desired, add more toppings like fresh cilantro, sliced jalapeños, avocado, and pepitas!