Heat the olive oil and butter in a pot over medium heat. Add the onions and garlic; sauté until golden brown.
Add the rice and stir around to toast the outside of the rice for about 2 minutes. Add 2 ladles of the broth and stir, bring to a simmer. Repeat this process adding a ladle or two of broth as it is absorbed by the rice until you have used almost all of the broth - it should take about 20-30 minutes.
Season the chicken on both sides with salt and pepper. Drizzle with oil.
Heat an oven safe grill pan over medium heat until hot. Cook the chicken on both sides to get nice golden brown markings. Transfer to the oven and cook until the internal temperature reaches 160°F. Set aside to rest for 5 minutes before cutting into bite sized pieces.
Once the rice is tender and creamy and most of the broth has been absorbed, stir in the butter, peas, and parmesan cheese. Remove from heat, season with salt and pepper as needed to taste. Stir in the chicken.
Garnish with parsley, and serve with bread.
Notes
Pro tip: to butterfly the chicken lay the breasts down on a cutting board and use a sharp knife parallel to the cutting board to slice them (carefully) in half.