Step 1

Turn on a multi-functional pressure cooker (such as Instant Pot®) and select Saute function. Pour in oil and heat until hot. Add carrots, celery, and red onion; cook until tender, 4 to 5 minutes. Season with parsley, basil, and pepper. Pour in chicken broth and add meatballs. Close and lock the lid. Close the valve and select the Soup function according to manufacturer's instructions; set timer for 3 minutes. Allow 10 to 15 minutes for pressure to build.

Step 2

Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid. Add pastina and stir to combine. Replace the lid. Close the valve and select the Soup function according to manufacturer's instructions; set timer for 3 minutes. Allow 10 to 15 minutes for pressure to build.

Step 3

Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Add spinach and stir. Let soup sit for 5 minutes so pasta will be fully cooked and spinach will be wilted. Season with salt to taste.

Step 4

Ladle into bowls and top with Parmesan cheese.