Use this basic ice cream soda recipe make a traditional ice cream soda. Simply put two to four tablespoonfuls of flavored fountain syrup into a tall, frosty soda glass. Carefully drizzle the flavored syrup down around the sides of the glass and then slowly fill the glass with chilled soda water to about 2 inches or so beneath its rim. Now add a large, round scoop of frozen vanilla ice cream so that it carefully rests directly on the rim of the glass allowing the ice cream and soda water to foam beneath.
The ice cream must be positioned on the glass just right: If it's resting too deep in the soda water the foam will overflow the glass; if it's situated too high on the rim there won't be enough foam produced to call it a true soda. With a bit of practice, you'll get it right. Insert a drinking straw and a long-handled spoon between the ice cream and the rim of the glass and top the beverage off with a garnish of whipped cream and a big red maraschino cherry.