Start by rolling your lemons on the counter while pressing down firmly. This breaks down the internal membranes and releases more juice. Cut each lemon in half and squeeze out every drop of that precious liquid. You'll need about 4-6 lemons to get one full cup of juice, depending on their size and juiciness.

In your large mixing bowl, pour the freshly squeezed lemon juice and the entire can of sweetened condensed milk. Using your wire whisk, blend these ingredients together until completely smooth and well combined. The mixture should have a beautiful pale yellow color and creamy consistency without any lumps or streaks.

Gradually add cold water to your lemon-condensed milk mixture, starting with 2 cups. Stir well after each addition and taste as you go. If the flavor is too strong or sweet, add more water until you reach your perfect balance. Remember, you can always add more water, but you can't take it away!

Grate the zest from one lemon directly into your mixture. This step adds incredible fresh citrus aroma and tiny bursts of intense lemon flavor. Mix gently to distribute the zest evenly throughout your lemonade.

Fill your large pitcher with plenty of ice cubes, then pour your lemonade mixture over the ice. Stir gently to combine and chill. Pour into individual glasses filled with fresh ice, and garnish each glass with a sprig of mint and a lemon slice.