Toast the Cashews: Add the cashews to a large skillet over medium-low heat. Toast for 4–6 minutes, stirring frequently, until golden and fragrant. Transfer to a plate and set aside.
Prepare the Sauce: In a small bowl, whisk together the soy sauce, maple syrup, rice vinegar, sesame oil, cornstarch, cold water, garlic and black pepper until smooth. Set aside.
Prepare the Tofu: Cut the tofu into bite-sized cubes or break it into pieces by hand. Transfer to a bowl, sprinkle with cornstarch, and season with salt and pepper. Toss until evenly coated.
Cook the Tofu: Heat 2 teaspoons of cooking oil in the skillet over medium-high heat. Add the tofu in a single layer and cook for 5–7 minutes, turning occasionally, until golden and crisp. Work in batches if needed to avoid overcrowding the pan. Transfer to a plate.
Cook the Vegetables: Add another 2 teaspoons of oil to the skillet. Add the carrot, onion, bell pepper and broccoli. Stir-fry for 5–7 minutes, stirring frequently, until tender-crisp.
Add the Sauce: Return the tofu to the skillet and add the toasted cashews and prepared sauce. Stir continuously for 1–3 minutes, until the sauce thickens and coats the tofu and vegetables. If the sauce becomes too thick, add a splash of water.
Serve: Serve immediately over rice, quinoa or noodles. Garnish with sliced green onions and chilli flakes, if desired.