In a large saucepan, whisk the milk and 1/2 cup of the heavy whipping cream together. Add the sugar. Turn on the heat to medium-low, and stir slowly. Do not turn the heat up, as you do not want to scald the milk in this stage!

Separate the egg yolks from the egg whites. Toss the egg whites. Place the egg yolks in a bowl, and add the additional 1/2 cup of heavy whipping cream. Using a whisk, stir until combined.

When the milk and cream are just bubbling around the sides of the saucepan and the middle has a faint ripple, temper the egg yolk mixture.

Once the yolks are tempered, begin whisking the mixture on the stovetop and slowly pour the yolk mixture in. Whisk constantly until the mixture has thickened.

Remove the saucepan from the heat, and stir in the vanilla and whiskey, whisking until incorporated.

Using a fine mesh strainer, strain the custard base to remove any lumps from the mixture. Pour into a glass or metal container to store overnight, and place a piece of plastic wrap on the surface of the custard. (Do not stretch it over the bowl, as a film will form on top of the custard.)

Refrigerate the custard overnight.

In the microwave, melt the dark chocolate with the butter. Stir every 30 seconds until smooth. Pour in the bourbon, then set aside.

On the stovetop, make the raspberry swirl. Bring the raspberries, water and sugar to a boil. When the sugar has dissolved, pour the mixture into a mixer. Mix until combined, then strain with a fine mesh strainer to remove all seeds.

Pour half the raspberry mixture into the chocolate mixture. Set aside.

Make the ice cream: Follow your ice cream maker's manufacturer's instructions.

When the ice cream has thickened, slowly drizzle in half of the chocolate mixture. Be sure to do this slowly and with a light drizzle, as you don't want big chunks of chocolate in the ice cream.

When the ice cream is finished in the ice cream maker, pour half of the mixture into a frozen loaf pan.

Drizzle the raspberry mixture, then the chocolate mixture over it.

Cover these with the other half of the ice cream, and top with more raspberry drizzle.

Use a knife to swirl the raspberry into the ice cream.

Finish the ice cream with the rest of the dark chocolate mixture drizzled on top of it.

Cover well with plastic wrap, and freeze for 4-6 hours, or until it is frozen solid.

Serve cold, and enjoy!