Preheat the oven to 160ºC fan/180ºC conventional oven. Grease and line a 2lb loaf tin with baking paper.
In a large bowl, cream the butter and golden caster sugar together until light and fluffy.
Beat in the eggs one at a time, adding one tablespoon of the 300 grams of flour with each egg to stop the mixture from curdling.
Stir the flour, cinnamon, mixed spice, hot chocolate powder and orange zest together in a separate bowl.
Tip the dry ingredients into the butter mixture and add the milk. Fold until smooth and combined. The mixture will be thick.
Fold in the sultanas.
Spread the mixture into the loaf tin and bake for 65-70 minutes. This time is a guideline as all ovens differ. Keep a close eye on the loaf cake after 65 minutes. When fully baked, the loaf cake should look golden brown and spring back when lightly pressed in the middle. When baked, remove it from the oven.
Leave the cake to cool in the tin for 15 minutes, then lift out and place onto a wire rack.
Heat the golden syrup in a small saucepan and whilst the cake is still warm, brush the top with a little warmed syrup, letting it sink into the sponge.
Leave the cake to cool completely.
To make the icing, first combine the hot chocolate powder and milk in a mug. Heat in the microwave for 20 seconds, then stir until smooth. Pour into a bowl and add the icing sugar and salt, and then mix until smooth.
Spread the icing on top of the loaf cake and decorate with the mini eggs. Slice the cake, and enjoy a piece with a cosy mug of Whittard Breakfast Tea!