In a small bowl, mix cornstarch with 1/4 cup water and stir to make a slurry. Set aside.
Place vegetable broth, mushrooms, 1/2 the green onions, bamboo shoots, soy sauce, vinegar, chili garlic sauce, ginger, salt and pepper into the Instant Pot. Stir.
Secure the lid, then turn pressure release valve to "sealing". Set to Pressure Cook on High and use manual (+/-) buttons to set time to 5 minutes. When cook time is complete, carefully turn pressure valve to "venting" for a quick release. Once pressure valve has dropped, remove lid and hit Cancel button. Press Saute button and adjust to High setting. Liquid will quickly start to bubble.
Stir cornstarch slurry into bubbling soup for 1 to 2 minutes until soup is thickened. Hit Keep Warm button. Gently stir in tofu, sesame oil and remaining green onions for 1 minute until warmed.
Serve topped with additional green onion slices and crispy wonton strips (optional).