In a medium bowl, whisk the egg yolks and ¼ cup brown sugar until combined.
In a medium sized, heavy bottomed saucepan, stir together cream, milk, salt, and remaining ¼ cup brown sugar. Bring to a simmer over medium-high heat, then reduce the heat to medium.
Carefully and slowly add a ladle-full of the hot cream mixture to the egg mixture, whisking the eggs constantly. Repeat with two more ladles of cream, adding slowly and whisking constantly. Using a heatproof rubber spatula, stir the cream mixture in the saucepan as you slowly add the egg mixture to the pan.
Cook the mixture over medium heat, stirring constantly, until it is thick, coats the back of a spatula, and holds a clear path when you run your finger across the spatula, about 2 minutes.
Pour the mixture through a fine mesh strainer into a zip top food storage bag. Seal the bag and place it in an ice-water bath, moving it around occasionally until cooled. Remove the container from the ice water bath and refrigerate for two hours or overnight.
Once the base is chilled, freeze in an ice cream maker according to manufacturer’s instructions.
While the ice cream is churning, make the mix-in. In a small bowl, combine honey and grape nuts. Once the ice cream is done in the ice cream machine, carefully fold in large chunks of the cereal mixture. Transfer the ice cream to a covered container and freeze for a minimum of four hours.
Homemade ice cream will stay good for about 1 week but is best enjoyed within a few days.
Temper the eggs - Make sure you’re whisking your eggs as you slowly add the hot cream so they don’t curdle. Running the finished custard through a fine mesh strainer will help remove any eggs that may curdle, but you really want all those eggs making your ice cream richer instead of getting strained out.
Stir the custard as it thickens - If you don’t stir, it will thicken from the bottom up, burn, and get lumpy.
Open your zip top food storage bag inside a glass measuring cup - This will allow it to stay open and hold its structure while you’re pouring the liquid in.
Chill more than you think you need to - Ice cream will be at its best if you chill as long or even more than recommended. All freezers perform differently, so use your senses to make sure your ice cream is frozen and ready to eat.
Tips for customizing brown sugar grape nut ice cream
Leave out the honey for more of a classic grape nut ice cream
Use your favorite vanilla vegan ice cream base to make this dairy-free and vegan
Sprinkle extra grape nuts over the top of ice cream before serving for extra crunch
Add a handful of mini chocolate chips with the grape nuts