Transfer the chicken to a large bowl and add the onion, egg, breadcrumbs, garlic, parsley, black pepper, thyme, chilli flakes and salt. Mix well, grease the palm of your hand with oil, and shape into balls. You would need approximately one tablespoon mixture to make one ball. 

Switch on your instant pot to sauté mode and heat the butter in the steel insert. Slide in the meatballs and fry on medium heat until golden brown. Remove onto a platter. Fry in batches if you have to. Cancel sauté. 

Spread the rice in a layer at the bottom of the steel insert. Arrange the fried meatballs in a single layer on top of the rice and pour the broth on top. Secure the lid, make sure the steam release handle is on 'sealing' and press the pressure cooking button (high). Set the timer to 5 minutes. When the timer goes off, wait ten minutes before releasing the steam and opening the pot. 

Garnish with the slivered almonds and tomatoes. Drizzle some melted butter mixed with extra parsley on top of the rice. Serve hot.