1 stick (115 g) unsalted butter, softened
1-1/3 cups (300 g) packed dark brown sugar
2 teaspoons (10 ml) pure vanilla extract
2 eggs, at room temperature
1 cup + 2 tablespoons (145 g) all-purpose flour
1/2 cup (60 g) Dutch-process dark cocoa powder
3/4 teaspoon (4 g) baking powder
3/4 teaspoon (6 g) kosher salt
3/4 cup (180 ml) buttermilk, shaken and warm
1/4 cup (60 ml) coffee or espresso
3 tablespoons (45 ml) mayonnaise
1/3 cup premium dark or extra dark chocolate chips
3/4 teaspoon baking soda
2 teaspoons (10 ml) white vinegar
2 tablespoons (30 ml) cold water
1-1/2 teaspoons unflavoured gelatin (such as Knox brand)
1-3/4 cups (420 ml) whipping cream (35-37% fat), cold, divided
3/4 cup (95 g) icing sugar
1 teaspoon (5 ml) pure vanilla extract
Pinch of salt
6 oz (180 g) premium dark or extra dark chocolate, chopped
1 stick (115 g) unsalted butter
1 tablespoon (15 ml) light corn syrup
Splash of liqueur of choice, optional (grand marnier, spiced rum, kahlua, etc.)
Pinch of sea salt (regular salt, if necessary)