Set 6-qt Instant Pot (or pressure cooker) to high "Sauté" setting. Add 1 tablespoon olive oil. Add onion and garlic, cook until onions turn transparent, about 2 minutes. Stir frequently.
Add bacon bits, potatoes, corn, vegetable broth, thyme and cayenne pepper. Season with kosher salt and ground pepper. Stir until well combined. Set Instant Pot (or pressure cooker) to the "Manual" setting, adjust pressure to "High" and set time to 10 minutes. Make sure pressure spout is set to "Sealed".
While soup is cooking, make the roux. In a small bowl, whisk together heavy cream and flour. Set aside.
When soup is finished, do a quick-release according to manufacturer's instructions. Change the pressure spout to "Venting" to allow pressure to release. Cancel the "Manual" setting and select the "Sauté" setting. Bring to a boil. Add roux mixture to soup. Cook and stir until it thickens slightly, about 3-4 minutes.
Serve immediately. Garnish with cheese and chives.