Peel and dice potatoes into about 2 inch pieces (I used medium potatoes and cut each into 6-8 pieces). Place diced potatoes in a large pot, cover with 6 cups cold water. Cover pot with lid and cook potatoes over medium high heat for 25 - 30 minutes until potatoes are very tender when pierced with a fork.
Meanwhile, steam broccoli by placing broccoli in a microwave safe bowl with 3/4 cup water and microwaving on high power for 4 - 5 minutes until very tender (alternately you can steam the broccoli in a steamer basket placed in a saucepan with water over the stove top until tender). Drain water from broccoli and dice broccoli into tiny pieces, set aside. Warm milk, cream and butter in a saucepan over the stove top or in the microwave in a microwave safe bowl.
Drain water from potatoes. Pour potatoes into a large mixing bowl. Mash potatoes very well with a potato masher. Add in warm milk mixture, sour cream, Cheddar Cheese, Parmesan Cheese, Romano Cheese, onion powder, garlic powder, salt and pepper then whip mixture with an electric mixer on medium speed about 1 - 2 minutes until fluffy and smooth. Fold in broccoli. Serve warm garnished with additional shredded Cheddar Cheese if desired.