First, chop the chocolate finely.

Then, bring the milk and heavy cream to a small simmer in a medium saucepot over medium-low heat. While the mixture is coming up to a simmer, whisk the egg yolks, sugar, and salt together in a large mixing bowl.

While whisking the yolk-sugar-salt mixture, slowly pour half the hot milk-cream mixture. Be sure to whisk the yolk-sugar mixture continuously to temper the yolks and prevent curdling. Pour the tempered mixture back into the pot, off the stove, adding it to the remaining milk-cream mixture. Whisk to combine.

Return the pot to the stove over low heat. Continuously scrape the bottom and edges of the saucepot and stir the mixture for even heating. Be careful not to overcook the mixture and curdle the eggs; you may need to remove the saucepot from the heat to prevent overcooking occasionally. Cook this mixture until an instant-read thermometer reads 85ºC or a clean line is left behind when you run your finger through the custard on the back of a wooden spoon, about 2 minutes. (If you do not have a thermometer, you can rely on the test of running your finger on the back of a wooden spoon.)

As soon as the custard reaches the proper temperature, remove the saucepot from the heat, and add the chopped chocolate. Whisk the mixture, taking care to get the corners of the saucepot, until all the chocolate is melted and evenly dispersed. The result should resemble a pudding.

Use an immersion blender to blend the mixture until it is homogenous, light, and aerated, and the chocolate is emulsified. The color of the mixture will lighten up from the blending.

Transfer the custard to a measuring cup with a spout, and divide the custard among ramekins, small glass jars, or classic single-serve “pots.” You can also store this in one large bowl and spoon it into small bowls when it is time to serve.