1. In a small saucepan, combine the water, sugar, and lemon peel. Stir and bring to a boil. Simmer for 3–4 minutes until the sugar dissolves. Remove from heat, let it cool, remove the peel, and add the limoncello if using.
2. Place the heavy cream in the bowl of a mixer and whip with the whisk attachment at medium speed until you have soft whipped cream, like a mousse. Be careful not to over-whip it until stiff. Transfer the whipped cream to a bowl. Place the mascarpone, powdered sugar, lemon zest, and vanilla in the mixer bowl. Beat until you have a smooth and creamy mixture.
3. Add the lemon juice and mix. Lower the mixer bowl and gently fold in the whipped cream. Add 1/3 of the whipped cream to the mascarpone mixture first, and use a spatula with circular motions to incorporate well, trying not to deflate the air from the whipped cream.
4. Repeat the same process with the remaining whipped cream. In a small bowl, thin the lemon curd with 2 tablespoons of the cold syrup so it becomes smoother and easier to spread.
5. Quickly dip the ladyfingers into the syrup (1 second per side) and arrange a first layer in a baking dish or glasses. Spread a layer of cream, sprinkle the thinned lemon curd thinly over it, and continue with a second layer of ladyfingers. Finish with cream. Cover and place the lemon tiramisu in the refrigerator for at least 4 hours, ideally overnight. When serving, garnish with the syrup peels, lemon zest, lemon curd, and mint leaves.
