In a heatproof bowl, melt the butter and both types of chocolate in the microwave or over a pan of simmering water.
Stir until smooth.
While the chocolate and butter mixture cools slightly, whisk the eggs and caster sugar in a large bowl using electric beaters until pale, fluffy, and doubled in volume.
Whisk in the melted chocolate.
Fold in the flour, cocoa powder, and mixed spice until no pockets of flour remain.
Pour the mixture into the prepared tin, level the top with a spatula, and bake for 20-25 minutes.
The top should be set and shiny but slightly wobbly.
Leave the brownie to cool completely in the tin, then chill in the fridge until set.
Step 2 – Decorate the Brownie:
While the brownie cools, brush the rosemary sprigs and glacé cherries with egg white, dab off the excess, and coat in caster sugar.
Let them dry on a wire rack.
Place the chocolate truffles on a sheet of baking paper or foil and spray with the edible gold lustre.
Dust the chilled brownie with icing sugar to create a snowy surface.
Top with crushed amaretti biscuit pieces.
Insert the crystallized rosemary sprigs at random intervals.
You can cut the brownie into pieces first and dust with icing sugar.
Nestle a glacé cherry or gold truffle alongside each rosemary sprig.
Add chocolate buttons and silver balls for additional decoration.
