Bring full teakettle of water to boil, then keep simmering over low flame while you assemble ingredients.
Preheat oven to 350 degrees.
In large mixing bowl, whisk eggs until well blended.
Add cooled mashed sweet potato, brown sugar, dry spices and vanilla and mix well with heavy spatula, pressing to remove any sweet potato lumps.
Add half-and-half in three additions, mixing well; mixture will appear watery, but it thickens nicely with baking.
Divide mixture into six 8-10 ounce oven ready ramekins and place cups in large roasting pan.
Pour hot water carefully until it reaches halfway up the sides of the ramekins; it is safest and easiest to place the roasting pan with custards on a partially pulled out oven rack and then slowly pour the hot water into the pan, then carefully slide the pan and rack into the oven.
Bake for 40-45 minutes or until custards are set.
Remove the ramekins from the roasting pan (carefully, with oven mitts) and let cool slightly before serving and garnishing.
To garnish, top each custard with a dollop of whipped cream and a sprinkle of the cinnamon/white pepper mixture.
Custards may be made up to one week ahead, and warmed briefly in a 350 oven until just hot; custards may also be served chilled, but mouth feel will improve with heating.