Preheat oven to 350F. Line a 9x13-inch baking pan with parchment paper and butter sides; set aside.

Place the eggs, sugar and vanilla into a mixer bowl and whisk until eggs are light, fluffy and almost white in color. In a small cup, dissolve the instant coffee in 2 tablespoons of water, then add to the eggs. Add the marmalade and sour cream and use a spatula to gently fold in the ingredients.

In a separate bowl, combine the dry ingredients: flour, cocoa powder and baking powder. Sift the dry ingredients into the batter in small batches. Fold in the flour completely after each addition; fold gently to keep the eggs as light and fluffy as possible.

Pour the cake batter into the prepared pan and spread evenly to the edges. Bake in preheated oven until top is completely set, about 30 minutes. Remove from oven onto wire rack to cool completely.

To prepare the ganache: heat the heavy cream until hot. Stir in the chocolate chips until a smooth ganache forms. Set into the refrigerator to set. Once cooled, use a flat spatula to spread the ganache over the top of the cake. Cut the sheet into small squares and top with orange candies, if desired. Store covered.