Peel and chop potatoes and place into a microwave-safe bowl with a 1/4 cup of water. Cover with plastic wrap and microwave for 10 minutes or until tender and easily pierced with a fork. Use caution when removing the plastic wrap as it will be extremely hot. Use a potato peeler to remove the outer layer of the broccoli stem and then cut the crown into small pieces. Slice the stem into thin rounds and place all into a second microwave-safe bowl with the remaining three tablespoons of water. Cover with plastic wrap and microwave for 5 minutes or until broccoli is tender. Drain potatoes and then mash with butter, careful to mash out all the lumps. Add in cheese, salt and garlic powder. Set aside.