This would be the recipe I use for a moderately shiny (not super shiny) pourable ganache (see Swamp Brothers’ Alligator cake). For a mirror like ganache I would use the one from Rose Levy Beranbaum’s book, “Heavenly Cakes.”
1/2 cup heavy cream
1 Tbsp corn syrup
1/4 cup whiskey or rum
10 oz dark chocolate chips or finely chopped dark chocolate
Bring the cream and corn syrup to a gentle boil in a small saucepan over medium heat. Place the chocolate in a bowl and pour half of he hot cream over the chocolate. Let the mixture stand for 2 minutes then stir the mixture slowly with a wire whisk. Add the remaining cream and whiskey and whisk slowly until smooth. Let the mixture cool slightly before pouring over a buttercream cake.