Place the milk chocolate chips into a large bowl and set a mesh strainer over the top.
Mix together the milk, sugar, and salt in a medium saucepan and warm over low heat. Whisk together the egg yolks in a medium-sized bowl. Pour the warm milk mixture into the egg yolks, whisking constantly, then scrape the entire mixture back into the saucepan.
Stir the mixture constantly over medium heat with a wooden spoon, scraping the bottom as you stir, until the mixture thickens and coats the spoon. I recommend using a thermometer and removing the mixture from the heat when it reaches between 170-175 degrees Fahrenheit.
Pour the custard through the strainer over the milk chocolate chips, then stir until the chocolate is melted. Once the mixture is smooth, whisk in the cream, Guinness, and vanilla. Stir until cool over an ice bath.
Chill the mixture thoroughly in the refrigerator, then freeze it in your ice cream maker according to the manufacturer's instructions. Add the mini chocolate chips in the last few minutes of the mixing process.
Recipe by 2 Sisters 2 Cities at http://www.2sisters2cities.com/2014/03/double-chocolate-guinness-ice-cream/