Add coffee grounds and milk to an air-tight container and allow to steep overnight, or until desired strength is achieved.
In a medium bowl, whisk together egg yolks and sugar until light and fluffy. Set aside.
Pour milk through a fine-mesh sieve to remove coffee grounds.
Add coffee-infused milk, cream, vanilla, and salt to a pot. Place over medium heat, stirring frequently, until warm and beginning to steam.
Slowly pour some of the warm milk mixture into the egg yolk mixture, while whisking constantly to temper the egg yolks. Continue until all of the milk has been added.
Pour the mixture back into the pot and cook over medium heat, stirring constantly. Cook until the mixture thickens and coats the back of a spoon well.
Pour the mixture through a fine-mesh sieve (optional) into a heat-safe container. Cover and let cool slightly at room temperature for 20 minutes. Then, place in the fridge and chill overnight, or until completely cold.
Churn ice cream according to manufacturer's instructions.
Fold the toffee pieces into the ice cream and transfer to an air-tight container. Cover, and freeze until firm.
Notes
Prepare Your Ice Cream Machine - If your ice cream machine has a bowl that needs to be frozen, remember to freeze it in advance so it's ready when you need it. I prefer to freeze it overnight to ensure it's fully frozen before using.Choosing the Right Coffee - The coffee that you choose directly impacts the flavor of the final ice cream. When you choose the coffee to use for this recipe, choose a coffee that you enjoy drinking.Coffee Strength - How strong you like your coffee is a personal preference that will determine how you'll like this ice cream. If you like strong coffee, steep the coffee and milk for a longer period of time. If you like mild coffee, steep for less time.Tempering the Egg Yolks - This step is important because it allows the eggs to heat up slowly, so they don't curdle and cause little egg lumps in your ice cream mixture.Cooking the Ice Cream - When cooking the ice cream, you'll know it's done when it coats the back of a spoon well. If you want to use a thermometer, it should reach this point around 160 - 180℉.Strainer - Pouring the cooked ice cream base through a strainer or fine-mesh sieve is optional, but it ensures that you don't end up with any lumps or pieces of cooked egg yolk in your mixture.Chilling the Mixture - I prefer to chill the ice cream base overnight to ensure it's fully cold and allow everything to meld together. If you don't want to wait that long to churn your ice cream, you can move onto the churning step once the ice cream base is fully cold.Serving - If the ice cream has been in the freezer for an extended period of time, you may want to let it sit out on the counter for a few minutes to allow it to soften slightly before scooping.Churning without an Ice Cream Machine - If you don't have an ice cream machine, I show an alternate method for churning ice cream here (https://brooksidekitchen.com/how-to-make-ice-cream-without-a-machine/).