Preheat your oven to 400°F (200°C). Cut the top off the garlic head, drizzle with olive oil, wrap it in foil, and roast for about 30 minutes.

While the garlic roasts, peel and chop the potatoes into even pieces. Place them in a large pot, cover with water, and add a generous pinch of salt. Bring to a boil and cook until fork-tender, about 15-20 minutes.

Drain the potatoes and return them to the pot. Squeeze the roasted garlic cloves into the potatoes, discarding the skins.

Add the butter, sour cream, and half of the shredded cheddar cheese.

Using a potato masher or mixer, mash the mixture until it reaches your desired creaminess. Season generously with salt and pepper, tasting as you go.

Stir in the remaining cheddar, allowing it to melt into the warm potatoes.

Transfer to a serving dish and sprinkle with chopped chives or parsley if desired.