Step 1

Bring 1/2 cup water and 1/2 cup granulated sugar to a simmer in a small saucepan over medium heat, stirring to dissolve the sugar. Remove from the heat and let cool to room temperature, at least 30 minutes. Meanwhile, juice 8 to 10 medium lemons until you have 1 cup juice.

Step 2

Pour the syrup and lemon juice in a blender and add 5 cups ice. Start blending on low speed and gradually increase the speed until completely blended and creamy. Pour into two glasses, garnish with a mint sprig if using, and serve immediately.