Step 1

To make the chocolate syrup, in a large bowl, whisk together the chocolate, boiling water, and simple syrup until smooth and pourable. Transfer to an airtight glass jar or bottle and seal. Store in the refrigerator until ready to use.

Step 2

To make an egg cream, pour the chocolate syrup into a tall glass, add the milk, then top with the seltzer. Stir to your desired level of smoothness.