In a small saucepan, combine the egg, sugar and salt. Add the milk and whisk to incorporate. Heat over medium heat until slightly thickened. The mixture should be thick enough to cover the back of a spoon.
Remove from heat. Add the chocolate chips and vanilla. Stir until the chocolate is completely melted. Pour into a serving dish or individual serving dishes and refrigerate at least 4 hours before serving. The mixture will seem pretty runny at this point but don’t worry, it really firms up as it rests in the refrigerator.
Notes
*Note – if you try this with another type of milk, such as 2%, I’d love to hear how it turns out!