Combine the eggs, sugar, chocolates, and salt in the blender and set aside.
Heat the milk in a small (1-quart) saucepan until it is scalding hot (180ºF).
Pour the milk into the blender with the other ingredients, then immediately blend on a medium setting until the chocolate has melted and the mixture is smooth. If necessary, scrape down the sides of the blender once or twice during blending.
Add the olive oil and orange zest to the blender, then blend on a low setting for two or three one-second pulses.
Pour the mixture into ramekins or other serving dishes. Chill for at least six hours, and garnish with sea salt crystals just before serving.