Blitz the graham crackers in a food processor until they have the consistency of bread crumbs.
Transfer to a bowl and stir in the melted butter until the mixture starts to come together.
Spoon this into an 8-inch/20 cm tart pan with a removable bottom and press into an even layer.
Transfer to the fridge to chill and set while you make the filling.
Put the dried limes in a small bag and crack them by hitting them with a rolling pin a few times until they break into small shards.
Transfer to a small saucepan and add the cream and sugar. Let infuse over low heat for 10 minutes, stirring occasionally.
Remove from the heat and let cool for 5 minutes.
To make the filling, melt the chocolate in the microwave or by placing it in a heatproof bowl set over a saucepan of simmering water.
Strain the lime-infused cream through a fine-mesh sieve into the chocolate and press against the pieces of dried lime with a wooden spoon to extract all their flavor.
Add the vanilla and a pinch of salt and whisk until you have a thick and glossy filling.
Remove the crust from the fridge and spoon the chocolate ganache into it.
Return it to the fridge and chill for at least 1 hour.
Smash the pistachios with a mortar and pestle and sprinkle over the tart along with rose petals before serving.
