Grease a 9-inch tart pan with a removable bottom.
Stir cookie crumbs, crust salt, and melted butter until the mixture looks like damp sand.
Press crumbs firmly into the bottom and up the sides of the pan. Chill while you make the filling.
Warm cream and orange zest in a small pot over medium heat until steaming. Remove from heat and let infuse 5 minutes.
Place chopped chocolate in a heatproof bowl. Rewarm the cream to a gentle simmer, then strain it over the chocolate.
Let sit 2 minutes, then whisk until smooth. Add butter, vanilla, orange juice, liqueur (if using), and filling salt; whisk until glossy.
Pour ganache into the crust and smooth the top. Tap the pan to release air bubbles.
Chill until fully set, 2–3 hours. Garnish with flaky salt and candied peel. Slice and serve with whipped cream.