Bring the heavy cream to a simmer in a heavy-bottomed saucepan over medium heat. Whisk together maple syrup or organic syrup, cornstarch, and egg yolks.
Pour about 1/3 of the hot cream into the syrup mixture, then pour the syrup mixture into the remaining cream in the saucepan.
Heat over medium-low heat, stirring constantly, until hot and thickened slightly. Do not let boil. Strain into a large mixing bowl.
Cool the mixture; whisk in milk and vanilla. Chill thoroughly, then freeze in an ice cream machine. Add pecans when almost frozen.