Press the saute function and add the olive oil. When the oil is hot, add the onion and saute until it is soft. Add the garlic and stir until fragrant, about 30 seconds.
Add the chicken oregano, salt, and pepper. Cook until it starts to turn white. Turn off the saute function.
Add the broth then scrape the bottom of the pot to loosen any cooked-on bits (this will prevent the burn notice).
Add the rice and push it down into the liquid. Place the lid on the Instant Pot and make sure the pressure valve is in the sealed position.
Set the function to high pressure for 4 minutes.
When finished cooking, allow the Instant Pot to release pressure naturally for 10 minutes.
While the rice is cooking, make the sauce. Melt the butter in a saucepan. Whisk in the flour and stir for 2 minutes to cook the flour mixture.
Slowly whisk in the milk, stirring as you go. Continue to whisk until the mixture is smooth and thick.
After 10 minutes of natural pressure release, let the rest of the pressure out of the Instant Pot manually.
Stir in the broccoli, cream sauce and 1-1/2 cups of the cheese. Sprinkle the rest of the cheese on top then immediately replace the lid. Do not turn the Instant Pot on. Just let the casserole sit with the lid closed for 10 minutes. The residual heat will cook the broccoli.
Video
Notes
Deglaze the pot: Add the broth to the hot Instant Pot and scrape the bottom to remove any cooked-on bits. This step helps prevent the burn message.Thaw frozen broccoli: If using frozen broccoli, thaw it first and drain any excess liquid before adding it to the pot.Use cooked broccoli as an alternative: You can add cooked broccoli at the end instead of raw. If you do, let the casserole sit for about 3 minutes, just long enough to melt the cheese.