No-Bake Chocolate Orange Tart

Name: No-Bake Chocolate Orange Tart
Prep time: 20 min
Total time: 20 min
Cuisine: American
Ingredients: 1 package Biscoff cookies (8.8 ounces/250 grams); 1 stick unsalted butter (melted); 1 cup heavy cream (250 ml, see note 1); 1 orange (zest only); 1½ cups semi-sweet dark chocolate (buttons/callets or bar, 55% (8.8 ounces/250 grams), see note 2); 2 tablespoons unsalted butter (1 ounce/30 grams); 1 pinch salt; 1 cup water; 1 cup granulated sugar; 1 orange (thinly sliced)