I actually think I prefer this to mashed potatoes, which is probably sacrilege.

half a large head of purple cauliflower
4 red potatoes, chopped
half a stick of butter
1/2 cup milk
salt and pepper
Melt butter in saucepan. Add cauliflower and braise over low heat until tender (start checking at 20 minutes or so).
While that’s happening, boil water in pot. Add potatoes and cook until tender. Drain.
Keep milk warm over low heat.
Combine potatoes and cauliflower/butter mixture. Mash with a potato masher. Slowly add milk and mashed to desired consistency. Season with salt and pepper and serve.