Place the egg yolks in a medium bowl and set aside. Combine the cream and cocoa powder in a medium saucepan over medium heat, and whisk together while the cream heats up. Continue to cook the cream and cocoa, whisking frequently, until the cocoa is blended in and the cream starts to boil. Let the cream simmer and boil for about a minute, whisking constantly. The mixture will start to get thicker.

Remove the pan from the heat and add the chopped unsweetened chocolate,, whisking it in until it’s melted and smooth. Pour the cream through a strainer into a large bowl or container.

Combine the milk, sugar, and salt in the same medium saucepan (no need to wash it first.) Bring the milk to a simmer, then when it just starts to come to a boil, remove the pan from the heat. Whisk the egg yolks while you slowly pour in about a third of the hot milk mixture, whisking constantly so the eggs heat up but don’t cook during the process.

Now return the saucepan to the heat and start whisking the milk while you pour in the hot egg mixture. Continue to whisk as the custard cooks, and cook it until it thickens slightly and coats the back of a spoon. If you want to use a candy thermometer, you’re shooting for 175 F (80C).

Take the pan from the heat and strain the ice cream custard through a fine mesh strainer into the bowl of chocolate cream. Whisk in the vanilla extract and mint extract, then continue to whisk occasionally as it cools. Once at room temperature, press a layer of cling wrap on top of the custard and refrigerate it until it’s completely chilled. (To speed up the process, you can place the bowl over an ice bath and whisk it as it cools down.)

While the custard chills, prepare the white chocolate swirl. Combine the cream and white chocolate in a bowl, and microwave in 30 second increments, stirring after every 30 seconds to prevent overheating. Once the white chocolate is melted, add the butter, salt, and 1/2 tsp mint extract, and whisk them in until you have a smooth, shiny mixture. Taste it and add more mint extract, if desired. Press a layer of cling wrap on top and either refrigerate it until it is the texture of peanut butter (about 30-45 minutes) or leave it at room temperature overnight to firm up.

When the custard is chilled and the white chocolate mint swirl is ready, place a 9×5 loaf pan in the freezer. Churn the ice cream according to your ice cream maker’s instructions. Gently stir in the chopped Oreos.

Scrape about a third of the ice cream into the cold loaf pan and smooth it into an even layer. Drizzle/spoon a third of the white chocolate swirl on top in a haphazard pattern. Top with half of the remaining ice cream, and continue to layer the ice cream and drizzled white chocolate. Finish off with a swirl of white chocolate, and smooth it into an even layer. Cover the ice cream with cling wrap, and return to the freezer to firm up completely.