Add water to the pot, make sure you use at least the minimum amount required for your pot size.
Place peeled and chopped potatoes in the Instant Pot and season with a bit of salt and some pepper.
Put the lid on, close it and set the valve to “Sealing” position.
Press the Manual button and using the +/- buttons set the cooking time to 12 minutes.
It may take a while for the pot to come to pressure, because of the high volume of potatoes. That is ok, make sure the valve is sealed.
Once the Instant Pot is done cooking and it beeps, do a Quick Pressure Release by turning the valve to Venting position.
Once the pressure has vented, open the lid, carefully remove the pot and drain the water, save about 1 cup.
Add back the pot to the cooker, and while the potatoes are still hot, add the butter and stir.
Heat the cream or milk in the microwave for 30 seconds and add it to the pot as well.
Use a potato masher to mash the potatoes right into the pot, add salt and pepper to taste. Add garlic powder if you are using it.
To make the potatoes fluffier, you can use a hand mixer to fluff them up.
If you want the potatoes thinner in texture, you can add a little of the reserved water or more milk or cream.
At this point, stir in the Ranch salad dressing if you want to make Ranch mashed potatoes.