In a shaker, combine the cognac, ginger syrup and lemon juice. Add ice.
Seal and shake vigorously for 10–12 seconds to blend and chill thoroughly.
Fill a highball glass with ice, packing it firmly to maintain carbonation.
Slowly pour the ginger beer along the side of the glass until full. Stir gently once to preserve the bubbles.
Slowly pour the ginger ale down the side of the glass until full. Stir gently once to avoid losing carbonation.
Twist a lemon peel over the glass to release its oils, then drop it into the drink along with a slice of fresh ginger.
