In a large pot, add the cubed kohlrabi and potatoes and cover with water. Bring to a boil and cook for 10 minutes, or until the potatoes and kohlrabi are tender.
Drain the potatoes and kohlrabi and place in a large bowl. Add the butter, garlic, milk, Parmesan cheese, parsley, and salt and pepper to the bowl and mash together until smooth.
Pour the mashed potato mixture into a 9x13-inch baking dish and spread it out evenly. Sprinkle the top with additional Parmesan cheese.
Bake in preheated oven for 30 minutes, or until the top is golden brown and bubbly.
Interesting Facts
Kohlrabi is a member of the cabbage family.
Kohlrabi is known for its sweet and nutty flavor.
Red potatoes are a great source of fiber and antioxidants.