Pour 1/2 inch of cold milk into a tall soda glass.
Add seltzer or club soda to within 1 inch of the top of the glass; stir vigorously with a long spoon (this will cause it to become white and bubbly with a good head of foam).
Very gently pour 2 tablespoons of chocolate syrup slowly down the inside of the glass; briskly stir with a long spoon only at the bottom of the glass where the chocolate sits. The resulting drink should have a dark brown bottom and a 1-inch high pure white foam top (if you mix it too much, the foam disappears).
NOTE: Drink Immediately! Do not let the prepared Egg Cream sit for a long period of time (5 minutes or more) as it will go flat.