Scrub sweet potato, and then slice ¼ off. Slice off ends and remove outer layers from onion. Cook sweet potato and onion in Instant Pot: pour 1 cup of water into Instant Pot, then place trivet in bowl. Place ¼ (or more) of the sweet potato and ¼ of the onion (or more) on top of the trivet.
Close lid, set vent to SEALING. Set MANUAL, select high pressure and set timer to 15 minutes. Cook. Turn knob to release steam immediately. Remove thyme sprigs.
Add sweet potato, onion, ¼ package silken tofu, ¼ cup stock, 1 teaspoon olive oil, and ¼ teaspoon salt to high powered blender (no need to chop or break anything up!). Select soup setting, blend. Transfer to serving bowl, serve immediately with crusty bread or your favorite rice.
Cook whole sweet potato and whole onion in the Instant Pot. You can use the remaining vegetables in other dishes like this harvest bowl and soups
The onion will become really soft if cooked with the sweet potato. This is fine for soup, or if you were to use the rest in a sauce-like tomato sauce.