I find using melted ice cream with milk and chocolate sauce adds extra flavor and richness to an egg cream. I drank these as a kid and really found them to be the perfect blend of sweet and bubbly. I come from a house where my father would keep the champagne for New Years in the freezer until we were ready to drink it. There were always little ice chips in it and I have really grown to love ice cold drinks of any kind. This recipe is no different. For me, all of the ingredients have to be very cold for optimum results.
Pour the syrup into the bottom of a glass. Add the skim milk and stir to blend slightly. Add the seltzer.;
In a small bowl, combine and whisk the cocoa powder, sugar, and salt with the water and vanilla extract. Transfer to a small saucepan and simmer over low heat until the ingredients meld together, 2 to 3 minutes. Set aside to cool. Refrigerate. Use as needed.
Use a wider glass to get more froth from the soda.