In a medium saucepan, combine the whole milk and heavy cream. Whisk in the cane sugar, unsweetened cocoa powder, and kosher salt until combined. Bring to a simmer over medium heat, whisking often until the sugar and cocoa powder are dissolved and the mixture is smooth.

Whisk the egg yolks in a separate bowl until combined. Once the milk and cream mixture is simmering, reserve ? cup of the mixture and reduce the heat to medium-low. Slowly pour the reserved mixture into the egg yolks while whisking constantly to temper them.

Slowly pour the tempered egg yolks into the saucepan with the remainder of the milk and cream mixture. Cook over medium-low heat for 5 to 10 minutes, whisking continuously until the budino thickens to coat the back of a spoon and reaches a temperature of at least 160? (71.1?).

Place the semi-sweet chocolate in a large bowl with a fine mesh strainer on top. Pour the hot budino through the strainer onto the chocolate, using a large, heat resistant spoon to help it pass through smoothly. Whisk the budino and chocolate together until the chocolate is fully melted and combined. Then whisk in the butter and vanilla extract.

Pour the budino equally into small ramekins or serving glasses. Cover and let cool to room temperature. Then chill in the refrigerator for at least 3 hours to set.

Remove the budino from the refrigerator and garnish with a dollop of whipped cream and chocolate shavings. Serve immediately.