In a medium saucepan, heat cream, milk, and sugar over medium heat. Stirring constantly, let mixture reach just the point of simmer before removing from heat.
Lightly whisk egg yolks in a separate medium bowl.
Slowly pour about half of the warm cream/milk mixture into the bowl with the yolks, whisking continuously. Then pour egg/cream mixture back into the saucepan with the rest of the cream mixture.
Continue to cook over low heat, while whisking. When the mixture thickens enough to coat the back of the spoon, after about 4-6 minutes, remove the saucepan from heat.
Pour cream mixture through a strainer into a large bowl. While mixture is still hot, stir in sweet potato puree, cinnamon, ginger, nutmeg, and salt until completely blended.
Cover bowl with plastic wrap so that plastic is touching top of cream mixture (this will prevent a skin from forming). Refrigerate until chilled, at least 4 hours.
Once mixture is chilled, freeze in an ice cream maker according to the manufacturer’s instructions. When ice cream is almost frozen, mix in white chocolate chips and toasted pecans.
When ice cream is frozen, remove to airtight containers and place in freezer for at least 4 hours to continue to harden.