Peel potatoes, rinse, cut into quarters.
In an Instant Pot ( or pressure cooker ) insert, add quartered potatoes, and 4 cups water or enough water to mostly cover potatoes.,
Turn device on. Secure lid. Set pressure valve to SEALING. Select MANUAL or PRESSURE COOK; cook on high-pressure 12 minutes. Pressure cooker will beep and indicate "ON" while it comes to pressure. It took mine about 15 minutes to come to pressure then it started to count down from 12 minutes.
Once done, select CANCEL. Do a QR or QUICK-RELEASE by turning steam release handle to release steam immediately. Once pressure pin drops, open lid and turn off the device.
Drain liquid or remove potatoes with a slotted spoon to a large bowl. Slightly mash potatoes with potato masher.
Add in 6 tablespoons butter, 3 teaspoons Lawry's seasoning salt, 1/2 teaspoon pepper, 1/4 teaspoon salt, and 1/3 cup milk or half & half.
Continue to mash potatoes to desired consistency while fully incorporating added ingredients. Add diced green onions if desired.