Step 1

In a saucepan, cover the potatoes with cold water and season generously with salt. Add the thyme and garlic, bring to a simmer and cook until tender, about 40 minutes. Drain well. Let the potatoes cool, then slip off and discard the skins.

Step 2

Using a ricer and working over a large bowl, rice the potatoes with half of the butter. Strain through a fine sieve into a large saucepan, pushing them through with a sturdy rubber spatula. Mix in the remaining butter and the heavy cream. Season with salt.