Prehead oven to 400 degrees. Cut off the top of the head of garlic to expose the open tips of the cloves. Place on a piece of aluminum foil and drizzle with 1-2 tbsp olive oil, making sure it soaks down into the open cloves. Wrap the foil around the head of garlic to make an enclosed foil packet, and roast in the oven for 30 minutes. Remove from oven to cool.
While garlic is roasting, cover the potato cubes with cold water in a large pot and put on the stove on high heat to boil. Once the water begins boiling, turn down the heat to medium high and continue boiling for 15-20 minutes or until potatoes pierce easily with a fork.
Drain the potatoes and return to the pot. Mash 4 cloves of the roasted garlic into a paste and mix into potatoes, along with chicken broth, cream, butter, 3-4 tbsp truffle oil, salt, and pepper. Mash until fluffy. Use more garlic if you'd like, (you have a whole head!) but beware of overpowering the truffle oil! - I'd taste it first as written before deciding whether to add any more.
Add more salt and pepper if you'd like, to taste. Drizzle a little extra truffle oil on top of the potatoes before serving, if desired.