How to Make It
Set a programmable electric pressure cooker (such as an Instant Pot) to SAUTE on normal heat. Add olive oil and onions and cook, stirring constantly, until softened and golden brown, 20 to 25 minutes. Add 1/4 cup water to loosen browned bits. Transfer onions to a small bowl and let cool completely, about 20 minutes.
While onions cool, pour 1 cup water into pot and insert wire metal steam rack. Place potatoes on rack. Cover Instant Pot, and fasten lid. Lock and seal steam valve. Set to HIGH pressure for 15 minutes. (The pot will take about 15 minutes to come up to pressure before the cooking program begins.) Allow pressure to naturally release for 15 minutes, then carefully release pressure by turning valve to VENT. (Steam is fully released when pressure valve drops.) Remove lid and transfer potatoes to serving plate.
Stir onions together with sour cream, yogurt, parsley, chives, salt, and pepper. Set aside. Cut a lengthwise slit in each potato. Gently squeeze potatoes at both ends to open. Top each potato with about 2 tablespoons sour cream mixture and top each potato with 2 teaspoons grated cheese. Garnish with chives, if desired.