
Place the lavender flowers in a heat-proof/cold-proof tempered glass bowl. Gently stir in the sugar. Using your fingers, gently rub the flowers into the sugar.
Pour 2 cups of boiling water into the bowl with the lavender and sugar. Gently, using a wooden spoon, stir until the sugar is dissolved. Cover for 30 minutes so the syrup can diffuse fully.
After 30 minutes, strain the syrup into a glass pitcher.
Stir in the lemon juice and then stir in another 2 cups of cold water. Adjust the lemonade for tartness. If too sweet, add more lemon juice. If too tart, add more sugar.
Serve immediately in glasses over ice. Garnish with lavender sprigs and thinly sliced lemons.