In a mortar or with the flat side of a chef’s knife, mash the garlic to a paste with a pinch of salt. Transfer to a medium bowl and add the Roquefort. Roughly mash the cheese with the back of a spoon. Stir in the crème fraîche or sour cream and several grinds of pepper, and then add the cream until the consistency is slightly thinner than sour cream. (It should cling to the vegetables nicely but not be thick and goopy.) Taste and add more salt and pepper if needed. Refrigerate until shortly before serving. (The dip will thicken in the refrigerator but will return to its original consistency as it comes to room temperature.)