Add 2 tablespoons unsalted butter to Instant Pot insert and set Instant Pot to Sauté mode. Let butter melt completely.
Once butter has melted, add 1 pound boneless, skinless chicken breast to insert. Cook chicken pieces 3 to 4 minutes, stirring occasionally, until chicken is cooked through and lightly browned. Note: internal temperature of chicken should reach 160° Fahrenheit.
Transfer cooked chicken pieces to large bowl and set aside.
Add 2 tablespoons unsalted butter to Instant Pot insert and let butter melt completely.
Once butter has melted, add 1 cup chopped white onion and stir to incorporate. Sauté onions, stirring occasionally, 4 minutes or until onions are translucent.
When onions are translucent, add ½ tablespoon minced fresh garlic to insert. Stir to incorporate, then sauté mixture 30 to 60 seconds or until garlic is fragrant.
Add 1 ½ cups arborio rice to insert. Stir ingredients together until rice is fully incorporated and coated in melted butter.
Add ½ cup dry white wine and 1 pinch saffron to Instant Pot insert and stir to incorporate, making sure to scrape up any ingredients that may have stuck to bottom of insert.
Simmer mixture 2 to 3 minutes.
After simmering mixture, add 4 cups chicken broth and stir to incorporate, again making sure to dislodge any ingredients that may have stuck to bottom or sides of insert.
Simmer mixture 1 minute. After 1 minute, secure lid on Instant Pot with vent in Sealing position.
Set Instant Pot to Manual High Pressure mode. Set cook time to 6 minutes. Instant Pot will pressurize and then 6-minute cook time will begin.
When 6-minute cook time ends, immediately and carefully Quick Release internal pressure. Remove lid from Instant Pot and set aside.
Stir rice mixture until all liquid is fully absorbed and mixture is creamy.
Add 1 cup grated fresh parmesan and 1 tablespoon unsalted butter to insert. Stir until ingredients are fully incorporated and parmesan is melted.
Once parmesan has melted, taste risotto and add 1 ½ teaspoons salt and ¼ teaspoon freshly cracked black pepper, adjusting amounts of each as desired. Stir well to incorporate.
Turn off Instant Pot. Return cooked chicken to Instant Pot insert. Gently fold chicken into risotto mixture and simmer just until chicken is warmed through.
Portion chicken risotto into serving bowls. Top with additional parmesan or finely chopped fresh parsley if desired. Serve warm.