Pour boiling water into a large heatproof pitcher. Add teabags and mint leaves; let stand for 5 minutes. Discard teabags and mint leaves.
Add frozen lemonade, sugar and cold water, mixing well. Serve over ice; garnish with mint sprigs.
A really neat way that Gooseberry showed this drink is to put each serving in mason jars, sealer lids and all, with a slice of lemon in each jar. Put all the jars in a bucket of ice and serve to your guests that way. Very impressive for a barbeque or gathering and a very inexpensive way to do it as well.