Peel and dice the potatoes and cook in lightly salted water until done.
Mash the beet with 6 tablespoons of its own juice.
Mash the potatoes and mix with the beet puree. If the mashed potatoes are not yet creamy enough, add some more beet juice or milk. Milk or cream can be used to influence the color of the puree if the red is too strong. Add butter, melt, stir in well and season the puree with pepper and salt.
This puree goes well with many fish and poultry dishes and brings a nice contrast as a complementary color to green vegetables.