In a tall 10-ounce soda glass, combine the lemonade concentrate and the 1 teaspoon ice cream. Add a little carbonated water to mix the lemonade and vanilla ice cream, stirring the drink with a long-handled spoon.
Top the drink with the 2 scoops of vanilla ice cream. Fill the glass with 1/2 to 3/4 cup carbonated water. Serve immediately. Makes 1 tall ice cream soda.