Finely chop the dark chocolate and place it in a medium, heatproof bowl.

Set a fine sieve over the bowl but slightly to the side for easy straining later.

In a separate medium bowl, whisk together the sugar and egg yolks until the mixture turns pale and slightly thickened.

Add the heavy cream, whole milk, and a pinch of salt to the egg mixture. Stir gently until fully combined.

Pour the mixture into a medium saucepan. Cook over medium-low heat, stirring constantly with a spatula or wooden spoon.

Continue stirring until the custard thickens enough to coat the back of the spoon, about 5 to 8 minutes. Do not let the mixture boil as it can cause the eggs to curdle.

Remove the custard from the heat and stir in the vanilla extract.

Pour the hot custard through the fine sieve over the chopped chocolate to catch any bits of cooked egg.

Let the mixture sit undisturbed for 1 to 2 minutes to allow the heat to melt the chocolate completely.

Gently stir the chocolate and custard together until smooth and fully blended. The result should be a velvety, glossy mixture.

Evenly divide the chocolate mixture between 4 to 5 small jars or ramekins.

Lightly tap each jar on the counter to release any trapped air bubbles for a perfectly smooth finish.

Let the jars sit at room temperature until completely cool.

Transfer to the refrigerator and chill for at least 4 hours or overnight for the custard to set properly.

Just before serving, sprinkle a pinch of coarse salt on top for contrast or add a dollop of unsweetened whipped cream for extra richness.