Spiced Polish Christmas cake

Cake layers

• 125 g unsalted butter, softened and cut into pieces
• 220 g dark brown sugar
• 250 g honey
• 2 eggs
• 25 g Christmas spice mix (see Tips)
• 500 g plain flour, plus extra to dust
• 2 tsp bicarbonate of soda

Sour cream filling

• 50 g freshly squeezed lemon juice
• 3 tsp gelatine powder
• 700 g sour cream
• 250 g mascarpone cheese
• 40 g icing sugar

Chocolate ganache

• 200 g dark chocolate, broken into pieces
• 160 g pouring (whipping) cream