Step 1

For the syrup: Bring sugar and water to a boil in a small saucepan, stirring until sugar dissolves. Remove from heat, add thyme leaves, cover and let stand 1 hour. Strain and refrigerate.

Step 2

For the cocktail: Fill mixing glass with ice, add gin, St Germain, thyme syrup, and lemon juice. Stir until cold. Strain into flute, top with sparkling wine and garnish with thyme sprig.