Place a steamer insert into a large pot that can fit all the potatoes and butternut. Add 1 inch (2.5cm) of water to the pot.

Scrub the potatoes clean, peel them and cut into about 1.5" chunks. Put them in a colander and rinse under cold water. Set aside.

Cut the stem and bottom part of the butternut squash off and then peel. Cut into about 1.5" (4cm) chunks. Set aside.

Bring the water to a boil and very carefully add the potatoes and butternut to the steaming basket. Cover the pot with a lid.

Turn the heat down to medium and steam for about 20-30 minutes or until tender. They should be fully cooked.

Once the potatoes are fully cooked, remove the steamer basket from the pot and drain the water from the pot. Give it a quick rinse and dry with a paper towel.

Add a tablespoon of butter to the pan and cook the garlic for a minute or two, over medium heat, until just starting to brown.

Put the potatoes back into the pot. With an electric hand mixer (turned off) or a potato masher, break up the large potato pieces first.

Add the remaining 1/3 cup butter (with a large spoon or silicone spatula) so that it coats the potatoes. It doesn't have to be perfectly mixed in - it just has to be melted and coat the potatoes.

Sprinkle 2 teaspoons of salt over the top.

Using an electric hand mixer, add half the cream, starting off on low so that the liquid doesn't fly everywhere. Gradually add the remaining cream.

Turn it up to high and beat until smooth and creamy.

Taste and add more salt, if needed.

Garnish with a dab of butter and a little sage. Best if served immediately, as with all mashed potatoes.

Refrigerate totally cooled leftovers in an airtight container for up to 4 days.