Preheat the oven to 200°C.
Toss the chicken in a bowl with the egg white and 1/2 teaspoon salt. Let sit covered for 10 minutes. Mix 2 teaspoons vegetable oil into the ground rice cereal, rubbing it in with your fingers. Dredge the chicken strips in the cereal. Place the coated strips in one layer on a rack set in a baking sheet and coat lightly with the nonstick cooking spray. Bake until the chicken has an internal temperature of 165 degrees F, about 20 minutes. Let rest for 5 minutes, then cut into large bite-size pieces.
Heat the remaining teaspoon of oil in a small saucepan over medium heat. Add the garlic, ginger and dried chillies. Stir for a couple of minutes, then add the chicken broth, soy sauce, agave and vinegar. Mix the corn starch with 3 tablespoons water, and whisk into the sauce. Simmer gently for 8 to 10 minutes. The sauce should be thick, but pourable. Keep warm.
Put the broccoli florets in a microwave-safe bowl with 2 tablespoons water. Cover loosely with plastic wrap and microwave until crisp-tender, about 3 minutes.
Divide the chicken and broccoli evenly among four plates and drizzle the sauce over the top. Serve the rice on the side. Garnish with the sliced spring onions.