Tie fresh sage leaves in two small bunches with cotton kitchen string. Whisk 1 cup of cream, milk, sugar, and salt in a small saucepan over medium heat. Sift the cocoa powder into the pan also and mix well. Add the sage leaves and stir. Heat, but do not boil. Remove from heat when the mixture starts to steam and bubbles first appear around the edges. 

Stir the chopped chocolate in the pot of cream; continue mixing until smooth. Let it stand for one hour. Then, strain the liquid through a fine-mesh strainer. Discard the sage leaves. Return liquid to the stove over medium heat until it’s warm again.

Whisk the egg yolks in a medium bowl. Next, temper the eggs by slowly pouring the warm liquid into the yolks while stirring gently yet continuously. Then, transfer the milk egg mixture back to the saucepan.

Continue stirring over low heat while scraping the sides and bottom frequently. Cook until a custard forms, about 5 to 7 minutes. An instant-read thermometer will read 170 degrees F. Otherwise, you’ll know it's thick enough when the mixture coats the back of your spoon. 

While the custard cooks, make an ice bath by filling the bottom of a large bowl with ice and placing a medium bowl inside, over the ice. Add the remaining 1 cup of cream to the empty medium bowl. Arrange a fine mesh strainer over it.

Once the custard is ready, pour it through the strainer into the cream. Mix cream and custard thoroughly; continue stirring until cooled. Cover with plastic wrap and refrigerate for at least 4 hours or overnight.

Finally, transfer to an ice cream maker and freeze according to the manufacturer's instructions.