Prepare the Nectarine Simple Syrup: In a small saucepan, combine 1 cup of water and 1 cup of sugar. Heat over medium heat, stirring until the sugar is completely dissolved.

Add the chopped nectarines to the saucepan. Bring the mixture to a gentle simmer and cook for about 5-7 minutes until the nectarines are slightly softened.

Remove the syrup from the heat. Let it steep for 10 minutes for maximum flavor. Strain the syrup into a jar, pressing gently on the solids to extract all liquid. Discard the solids. Let the syrup cool completely.

In a large pitcher, combine the cooled Nectarine Simple Syrup, 1 cup of fresh lemon juice, and 4 cups of cold water. Stir well to combine.

Muddle a few mint leaves in the bottom of serving glasses. Fill glasses with ice, then pour the lemonade over the mint.

Taste and adjust sweetness or tartness as needed (add more syrup or lemon juice). Garnish each glass with a thin slice of nectarine and a sprig of fresh mint before serving.