1 cup whole milk
¾ cup sugar
2 cups heavy cream
Pinch of salt
1 vanilla bean, split in half lengthwise
6 large egg yolks
¾ tsp. vanilla extract
1 cup M&Ms
Combine the milk, sugar and 1 cup of the cream in a medium saucepan. Heat over medium-high heat, stirring occasionally, until warmed through. Scrape the seeds from the vanilla bean into the mixture and add the husk of the bean as well. Cover the saucepan, remove from the heat and set aside to steep for 30 minutes at room temperature.
Pour the remaining 1 cup of cream into a large bowl with a fine mesh sieve set over the top. In a separate medium bowl, whisk together the egg yolks. Slowly pour some of the warm milk mixture into the bowl with the egg yolks, whisking constantly to temper the eggs. Continue until you have added all of the milk mixture. Return the mixture to the saucepan.
Stir the mixture constantly over medium heat with a heatproof spatula, being sure to scrape the bottom of the pan as you stir. Continue cooking until the mixture thickens and coats the back of a spoon (about 170-175°F.) Pour the custard through the mesh sieve and stir it into the cream. Place the vanilla bean into the custard mixture, stir in the vanilla extract, and stir until cool over an ice bath. Cover and chill thoroughly in the refrigerator.
At least 1 hour before you are ready to freeze your ice cream, place the M&Ms in the freezer. Remove the vanilla bean from the ice cream batter, stir well, and freeze in your ice cream maker according to the manufacturer’s instructions. Transfer about one third of the ice cream to a freezer-safe air-tight container. Top with about a third of the frozen M&Ms and gently fold them in to the ice cream with a spatula. Repeat this layering and folding process until all the ice cream is in the container and all the candy has been incorporated. Freeze until ready to serve.