In a medium saucepan, combine heavy cream and whole milk over medium heat. Stir gently until small bubbles form, about 5-6 minutes. Remove from heat and cool slightly.

In a bowl, whisk together egg yolks, granulated sugar, and brown sugar until pale and creamy, about 2-3 minutes.

Slowly add half of the warm cream mixture into the egg yolk mixture, whisking continually. Pour this back into the saucepan with the remaining mixture.

Return to low heat, stirring constantly, cook until thickened enough to coat the back of a spoon, about 6-8 minutes.

Strain the custard through a fine-mesh sieve into a clean bowl. Stir in vanilla extract and a pinch of salt. Chill in the refrigerator for at least 4 hours, ideally overnight.

Melt unsalted butter in a skillet over medium heat, add chopped pecans, and toast until golden and fragrant, about 3-4 minutes. Let cool.

Pour chilled custard into an ice cream maker. Churn for about 20-25 minutes, adding toasted pecans in the last few minutes.

Transfer churned ice cream to a freezer-safe container, cover tightly, and freeze for at least 4 hours until firm.