Place the potatoes into the pressure cooker and cover with cold water and a pinch of salt.
Place and lock the lid into place and set the valve to sealed. Set to manually pressure cook for 9 minutes.
Once 9 minutes is done, turn the vent to release the pressure.
Once pressure has released, drain the water and add the Marmite to the potatoes. Mash until creamy and add salt and pepper, to taste. It may not need much salt due to the Marmite, so add a little at a time.