We recommend using one of our favorite dark chocolates - Callebaut Intense Dark Chocolate, L-60-40NV, or Ghirardelli Bitterweet Chocolate Baking Bar. If you like, garnish the pudding with whipped cream and chocolate shavings.
2 teaspoons vanilla extract
1/2 teaspoon espresso powder
1/2 cup (3.5 ounces sugar)
3 tablespoons Dutch-processed cocoa
2 tablespoons cornstarch
1/4 teaspoon salt
3 large egg yolks
1/2 cup heavy cream
2 1/2 cups whole milk
5 tablespoons unsalted butter, cut into 8 pieces
4 ounces bittersweet chocolate, chopped fine
Stir together vanilla and espresso powder in bowl; set aside. Whisk sugar, cocoa, cornstarch, and salt together in large saucepan. Whisk in yolks and cream until fully incorporated, making sure to scrape corners of saucepan. Whisk in milk until incorporated.
Place saucepan over medium heat; cook, whisking constantly, until mixture is thickened and bubbling over entire surface, 5 to 8 minutes. Cook 30 seconds longer, remove from heat, add butter and chocolate, and whisk until melted and fully incorporated. Whisk in vanilla mixture.
Pour pudding through fine-mesh strainer into bowl. Press lightly greased parchment paper against surface of pudding, and place in refrigerator to cool, at least 4 hours. Whisk pudding briefly and serve.