For the brownies:
8 tbsp. unsalted butter, cut into pieces
4 oz. unsweetened chocolate, chopped
1¼ cups sugar
2 large eggs
1 tsp. vanilla extract
½ cup all-purpose flour
Pinch of salt
½ cup semisweet or bittersweet chocolate chips
For the ice cream:
8 oz. milk chocolate (at least 30% cacao solids), finely chopped
1½ cups heavy cream
1½ cups whole milk
¾ cup sugar
Pinch of salt
4 large egg yolks
To make the brownies, preheat the oven to 350˚ F. Line an 8 x 8-inch baking pan with aluminum foil. Lightly grease the foil with nonstick spray. Add the butter to a small saucepan and melt. Whisk in the chopped chocolate and stir just until melted. Remove from the heat and whisk in the sugar, eggs and vanilla. Stir in the flour and salt. Fold in the chocolate chips with a spatula. Smooth the batter into the prepared baking dish. Bake for 30 minutes, until the center feels just set. Remove from the oven and let cool completely. Cut into small bits to be mixed into the ice cream. (Only half of the brownies are needed for the ice cream. The remainder can be eaten whole or frozen for later use.)
To make the ice cream, combine the milk chocolate and heavy cream in a heatproof bowl set over a pan of simmering water. Heat, stirring occasionally, until the chocolate is completely melted and smooth. Remove from the heat and set a mesh sieve over the top of the bowl.
In a medium saucepan, combine the milk, sugar and salt. Heat until the sugar is dissolved. In a medium bowl, whisk together the egg yolks. When the milk mixture is warm, slowly add to the bowl with the beaten egg yolks, whisking constantly. Return the mixture to the saucepan and continue to heat, stirring constantly, until the mixture thickens just slightly and coats the back of a spoon (170-175˚ F on an instant-read thermometer). Remove from the heat and pour the custard through the strainer into the milk chocolate mixture.
Cover and chill the mixture thoroughly in the refrigerator. Freeze the batter in an ice cream maker according to the manufacturer’s instructions. Once frozen, fold in the brownie bits with a spatula. Transfer to an airtight container and freeze until ready to serve.