Step 1 Place the ground chocolate in a large bowl.
Step 2 In a heavy-bottomed saucepan, combine the milk and cream, and bring to a boil over high heat.
Step 3Meanwhile, in a separate bowl, whisk together the sugar and egg yolks. When the milk mixture comes to a boil, remove from heat and slowly drizzle it into the bowl with the eggs while whisking to warm, or temper, the eggs.
Step 4Pour the mixture back into the saucepan and gently heat until it thickens to form a custard, stirring constantly with a rubber spatula. Remove from heat again, and pour the custard over the chocolate.
Step 5 Cover the chocolate bowl with plastic wrap for one minute to retain the heat and to give the custard time to begin melting the chocolate. After a minute, remove the plastic and gently stir the mixture to melt the chocolate into the custard. Continue stirring until the chocolate is emulsified with the custard.
Step 6Cover the chocolate custard with plastic wrap, pressing it against the surface (this will prevent a skin from forming), and place the custard in the refrigerator to chill overnight.