Place all ingredients for the sweet potato puree in sauce pan and cook down by almost half. Set aside, let cool completely.
Pour heavy cream into a heavy bottom sauce pan. Place over medium low heat, stirring frequently, turn heat to low.
Whisk together the egg yolks, sugar and salt in a large bowl until throughly combined.
Slowly pour about 1/ 2 CUP of hot cream mixture into the egg yolk mixture, whisk constantly. Repeat 3 more times whisking throughly before adding each additional 1/2 CUP of hot cream to the egg yolk mixture.
P our egg yolk mixture back into the saucepan with the remaining hot cream and whisk constantly until thickened and coats the back of the spoon, about 5 to 8 minutes. DO NOT LET MIXTURE BOIL I . E . BREAKDOWN.
Cool completely and incorporate puree with cream mixture.
Place in fridge and chill overnight.
The next day pour into the ice cream maker and freeze according to the manufacturer instructions. Remove the ice cream, pack into covered container and freeze 2 hours or overnight before serving.