Fill a large pot with cold water about half way and add the chicken broth. Peel the potatoes and then cut into large cubes, about 1 1/2-inches in size. Place the potatoes into the pot, then season the pot with salt and add the thyme and bay leaves. Cover the pot and bring the potatoes to a boil. Simmer over medium-high heat for about 20 minutes, or until the potatoes are fork tender. Larger pieces will need more time; smaller ones will need less time.

Drain the potatoes and remove the thyme bundle and the bay leaves. Cube the butter and add to the potatoes. Cover the pot for a few minutes and allow the butter to melt.

Next, add in 1/2 cup cream, nutmeg and a bit of ground black pepper. Use a potato mash and mash the potatoes for a few minutes, until a smooth and creamy puree forms. Add more cream if necessary, puree should be smooth but not too runny or too dry. For even fluffier potatoes, whisk the puree with a large whisk for 1 minute. Taste the sweet potatoes and season to taste with salt.