Pour the heavy cream and whole milk into a large saucepan and set it over medium heat until the surface just begins to bubble at the edges. Look for small bubbles ringing the pan and steam rising, not a rolling boil.

Whisk the egg yolks with the granulated sugar and brown sugar in a large bowl until the mixture loosens and lightens. The yolks should look glossy and slightly paler once the sugar dissolves into them.

While whisking hard, stream 1/2 cup of the hot dairy into the yolks, then add another cup in 1/2 cup additions, whisking the entire time. The bowl warms gradually and the mixture stays smooth with no visible flecks of cooked egg.

Return the tempered yolk mixture to the saucepan with the remaining dairy and cook about 5 minutes, stirring, until it thickens slightly. Dip a spoon in and swipe a finger across the back, the line should hold clean without the custard running back over it.

Strain the custard through a fine-mesh sieve into a large bowl, then stir in the vanilla extract and salt. Anything the sieve catches is exactly what would have turned into gritty specks in the finished ice cream.

Set the bowl inside a second bowl filled with ice and water and let it sit about 10 minutes, stirring now and then. The custard should feel cool against the back of your hand and thicken noticeably as it drops in temperature.

Cover the bowl and refrigerate it for at least 2 hours. A properly chilled base feels cold straight through and coats the spoon thickly.

Combine the chopped pecans, unsalted butter, and salt in a saute pan over medium heat, stirring constantly until the butter melts and the nuts toast. You will smell a deep, roasted, almost caramel aroma and the pecans will darken a shade.

Strain off the butter and spread the pecans out to cool to room temperature. Cooled pecans feel dry and snap cleanly instead of bending.

Pour the chilled custard into your ice cream maker and churn according to the manufacturer directions, roughly 30 minutes. The base thickens to soft-serve consistency and holds ridges from the paddle.

Add the cooled buttered pecans and churn another 5 minutes until they distribute evenly. The nuts should be suspended throughout rather than sinking to the bottom.

Transfer the ice cream to a 1.5 to 2 quart pan, cover it with plastic wrap or foil, and freeze at least 6 hours or overnight. It is ready when a scoop holds its shape without slumping.