In a medium saucepan, combine the whole milk, heavy cream, 1 cup of sugar, and a pinch of salt. Heat until hot but not boiling.
Whisk the egg yolks with the remaining 1/4 cup of sugar until pale and thick.
Temper the eggs by slowly adding about 1/2 cup of the hot milk mixture while whisking constantly.
Pour the tempered egg mixture back into the saucepan and cook until thickened, stirring constantly.
Remove from heat and stir in the teaberry extract.
Strain the custard, cool to room temperature, then refrigerate for at least 4 hours or overnight.
Churn the chilled custard in an ice cream maker according to the manufacturer’s instructions.
Transfer to an airtight container and freeze for at least 2 hours before serving.