Preheat the oven to 425°F. Line a baking sheet with parchment paper for the broccoli.
In a small bowl, squeeze the juice of the orange and reserve the zest for later. Mix the orange juice with the low sodium soy sauce.
In a separate bowl, combine the egg white and cornstarch. Add the orange mixture and whisk until fully integrated.
Place the chicken breast in a shallow dish and pour the marinade over it, ensuring it's well coated. Let it sit for 10-15 minutes to absorb the flavors.
While the chicken marinates, toss the chopped broccoli lightly with olive oil, salt, and pepper, and spread it evenly on the prepared baking sheet.
Place the broccoli in the preheated oven and roast for about 15-18 minutes, or until tender and slightly crispy at the edges.
Preheat an oven-safe skillet over medium-high heat. Add the marinated chicken breast and sear each side for 2-3 minutes until a light golden crust forms.
Transfer the skillet with the chicken to the oven and bake for an additional 8-10 minutes, or until the chicken is cooked through.
Remove the chicken from the oven, sprinkle with fresh orange zest for an extra burst of citrus flavor, and serve alongside the roasted broccoli.