• Preheat the oven to 170°C/Gas Mark 3.
• Grease an 18cm topsy-turvy cake tin or a 20cm round deep cake tin.
• Line the base with baking parchment and flour the sides.
• Melt the chopped chocolate in a microwave or over a pan of simmering water.
• Ensure the water doesn’t touch the base of the bowl.
• In a large mixing bowl, beat the butter and caster sugar together using an electric mixer until light and fluffy.
• Lightly beat the eggs with the vanilla extract and gradually add them to the butter mixture, beating well after each addition.
• Stir in the melted chocolate, followed by the mashed potato.
• Sift together the plain flour, baking powder, bicarbonate of soda, and salt.
• Fold these dry ingredients into the batter alternately with the buttermilk using a large metal spoon.
• Fold in the dark chocolate chips, then transfer the mixture to the prepared tin, leveling the top with a spatula.
• Bake for 25–30 minutes, or until the cake springs back when lightly pressed.
• Cool in the tin for 5 minutes, then turn out onto a wire rack to cool completely.

Make the Chocolate Ganache:

• Place the chopped chocolate in a small bowl.
• Bring the cream to a boil and pour it over the chocolate.
• Let it stand for 1 minute, then whisk gently until smooth and shiny.
• Mix in the Baileys Irish Cream.
• Set aside at room temperature to cool and thicken.

Prepare the Chocolate Glaze:

• Soak the gelatine leaves in cold water for about 5 minutes until soft.
• Sift the cocoa powder into a bowl and whisk in the water to form a smooth paste.
• In a pan, bring the double cream and caster sugar to a boil, stirring to dissolve the sugar.
• Remove from heat and whisk in the cocoa paste.
• Gently squeeze the excess water from the gelatine leaves and add them to the pan.
• Whisk until fully dissolved.
• Strain the mixture through a fine sieve into a bowl and cover the surface with cling film.
• Allow to cool.

Prepare the Baileys Cream:

• Whisk the double cream, Baileys Irish Cream, and vanilla extract together until medium peaks form.

Assemble the Cake:

• Once the cake has cooled, cut it horizontally in half.
• Spread the Baileys cream evenly over the bottom layer, then place the top layer back on.
• The ganache should now be thick enough to coat the cake.
• If not, refrigerate until it thickens but remains spreadable.
• Using a palette knife, coat the outside of the cake with the ganache, smoothing the surface.
• Refrigerate for 1 hour to firm up.

Apply the Chocolate Glaze:

• Ensure the glaze is cool but still liquid.
• If it has solidified, gently warm it over a pan of simmering water.
• Place the cake on a wire rack over a clean tray.
• Pour the glaze over the center of the cake, allowing it to flow evenly over the sides.
• Let the cake sit on the wire rack for 10 minutes, then transfer to a serving plate.

Decorate and Serve:

• Decorate the cake with mixed fresh berries.
• Serve and enjoy!