If you are making your own pesto, choose from one of the recipes linked above, or follow your own recipe.
In a large skillet, heat olive oil. Season the chicken with salt and black pepper each side, then use tongs to place in the skillet. Cook both sides for 6-8 minutes, depending upon the size of your chicken breast or fillets, or until cooked through to 165F at their deepest point. Set aside on a plate.
Once cool enough to handle, use two forks to shred the chicken.
Pour your chicken stock into a pot, heat to a low simmer and then keep warm in the pot.
Fry the onion, leek and garlic in the skillet (no need to clean first) for 4-5 minutes or until the onion has softened.
Tip in the rice, and toast for 1-2 minutes, stirring to ensure it doesn't burn. Ladle in the stock about ¼ cup at a time, adding more once it has been absorbed by the rice. Stir the risotto frequently, moving the rice around in the skillet.
After 10 minutes, add in the broccoli florets. Continue to ladle the stock into the skillet a ladle at a time, for another 10 minutes or until the rice has cooked through.
Add the chicken, pesto and apple cider vinegar and stir to combine into the rice. Warm through for a few minutes. Season with salt and black pepper, if using, then ladle into your serving bowls. Serve immediately.