Combine the strawberries, sugar and 5 cups water in a medium saucepan. Bring to a gentle simmer and cook for 30 minutes. Pour the mixture through a sieve and, using the back of a spoon, gently squeeze the juices from the strawberries. Stir in the lemon juice. Allow the mixture to cool for 15 minutes. Taste and add more sugar and lemon juice as you like. (How much sugar you need to add will depend on the sweetness of your strawberries.)
Serve in a pitcher with ice, garnished with some quartered strawberries and a few mint sprigs. It's so refreshing on a warm summer day.
This lemonade is also great as a base for a fun cocktail. In a tall glass with ice, add a shot of vodka, fill until about 3/4 with the lemonade and then top off with sparkling water. Garnish with strawberries and mint. It's great for the adults in the group.