Japanese Calpis Yogurt-Flavored Drink - cooking recipe

Ingredients

1 pint plain yogurt
2 1/2 cups sugar
1 1/2 teaspoons citric acid, powder (if you're using lemons, you'll need a lot of lemons to get the strong acidity needed. the result is) or 9 tablespoons lemon juice (if you're using lemons, you'll need a lot of lemons to get the strong acidity needed. the result is)
1 teaspoon vanilla extract

Preparation

Mix in a double boiler the yogurt and the sugar.
Heat the mixture while constantly stirring for about 15 minutes at 160 degrees F to 175 degrees F. Never let it boil!
When the syrup is at room temperature, add the citric acid powder and vanilla extract.
For serving, dilute the syrup with 3 or 4 times more of water or club soda (carbonated water) to your taste. Serve with ice.
Note: If you buy Calpico, don't mix it using the instructions on the bottle! The recommended proportions are much too strong, and it would be best to cut the amount in half.