Set your Instant Pot to the saute mode and heat the oil or butter. Add in the diced onion and sauté till translucent.
Add in the carrots, broccoli, and sauté the vegetables.
Add water and broth base. Cover the Instant Pot and secure the lid and set the valve in the sealing position.
Pressure cook for 1 minute. Wait for natural pressure release.
Meanwhile, mix the melted butter with flour and keep ready. Slowly whisk in the flour to avoid any lumps. The mixture should be creamy.
After opening the instant pot, lightly crush your veggies. This step is optional. Add half and half and let the soup boil in the sauté mode. Now add the flour and butter mixture and bring the soup to a boil.
Add cheese and mix well. Simmer the mixture for about two minutes and adjust salt and pepper.
The instant pot broccoli cheddar soup is ready.
Ladle into bowls and add cheese while serving.
Serve with French bread slices. Enjoy!