- Place potatoes, cauliflower, chicken broth, and salt to taste in a large pot, with the rosemary sprig on top.
- Bring to a boil, cover, and simmer for 20 minutes (or until potatoes are fork-tender).
- Remove from heat and remove and discard rosemary sprig.
- Drain potatoes and cauliflower and return to pot.
- Add the butter and use a potato masher to mash the vegetables with the butter until butter is fully melted.
- Add the milk and continue mashing until well combined. Use more milk if a creamier texture is desired. Adjust with salt to taste if needed.
- Serve garnished with parsley and pepper, if desired.
For a dairy-free or paleo version, make sure to use ghee instead of butter and use broth instead of milk (you can reserve one cup of the liquid you boiled it in for this).
For a vegan version, use olive oil instead of butter, and vegetable broth instead of chicken broth/milk.