Preheat your oven to 180°C (350°F) and generously grease a 9x13 inch baking tray with butter or line it with parchment paper for easy removal.
In a large mixing bowl, combine the softened butter and brown sugar. Using an electric mixer or whisk, cream them together on medium speed until the mixture is light, fluffy, and pale in color.
Crack and add the eggs one at a time to the mixture, ensuring each egg is fully incorporated before adding the next.
In a separate bowl, sift together the all-purpose flour, baking powder, and mixed spice powder.
Gradually fold the dry ingredients into the wet mixture using a spatula, incorporating them gently until just combined.
Carefully fold in the mixed dried fruits, chopped candied orange peel, and sliced almonds.
Pour the delicious batter into the prepared baking tray, using a spatula to spread it evenly and smooth the top.
Place the tray into the preheated oven and bake for 25-30 minutes. Perform the toothpick test to check if the cake is done.
Once baked, allow the traybake to cool in the tray for about 10 minutes, then gently transfer it to a wire rack to cool completely.
While the cake cools, prepare the cream cheese frosting. In a small bowl, beat the softened cream cheese with a mixer until smooth and creamy.
Gradually add the sifted icing sugar, orange zest, and orange juice, mixing until well combined and fluffy.
Once the traybake has completely cooled, generously spread the cream cheese frosting over the top.
Notes
For a festive display, cut the traybake into generous squares and garnish with sliced almonds and edible glitter.