If making sweet potatoes, preheat the oven to 450F or 425F convection. Line a baking sheet with parchment paper. Add the sweet potatoes, oil and salt and toss to coat. Bake for 10-15 minutes, or until cooked through and browned in spots.
In a large nonstick skillet over medium-high heat, add 1 tablespoon oil. Once the oil is hot and shimmering, add the white parts of the scallions, mushrooms, and salt. Cook for 5 minutes, stirring occasionally, or until the mushrooms are cooked through. Add the garlic, ginger, and red pepper flakes and cook for 30 seconds, stirring constantly. Transfer the mixture to a bowl.
Carefully wipe out the skillet and return to medium-high heat. Add the remaining 1 tablespoon oil and swirl to coat. Add the chicken and cook, breaking it up into chunks and spreading it out into an even layer, until cooked through, about 3-5 minutes. You want small chicken crumbles by the end!
Add the mushroom mixture back to the skillet and stir in the soy sauce or tamari and lime juice and cook for 30 seconds, stirring constantly. Remove from heat and stir in the green parts of the scallions and half of the nuts.
Add sweet potatoes and chicken to your cabbage cups and top with remaining nuts, avocado (if using), and a squeeze of lime.