DOUBLE CHOCOLATE METHOD

1. Important: it is important that the frosting isn't too cold for this version as the chocolate will seize when you add it. Make sure cream is very room temperature or slightly warm,  and butter is very room temperature. In winter I like to gently warm the cream before starting to make the buttercream as my house is cold. 
2. Roughly chop the chocolate and place in a heatproof bowl. Melt either in 30 second increments in the microwave, stirring between each, or over a double boiler until fully melted. Set aside to cool to room temperature - do not let it cool too much, I like to melt it and then start to make my buttercream. 
3. In the bowl of a stand mixer using the whisk attachment, beat the butter, heavy cream, golden syrup, salt, and vanilla together on medium to high speed until light and fluffy and significantly increased in volume and lightened in colour. 
4. Add the powdered sugar and cocoa powder and mix on low to incorporate, then increase the speed of the mixer to combine fully. Add the melted chocolate, and mix again to incorporate. 
5. If your buttercream consistency is not to your liking (you want it a little softer and fluffier), you can add warm cream 1 Tbsp at a time, beating well after each addition and adjusting if necessary until the desired consistency is reached. I find that I do not usually need to add extra cream. 
6. Switch to the paddle attachment and mix on low speed for about 5 minutes to remove any large air bubbles. 
7. Use immediately - this is a crusting buttercream so it will set. Leftovers can be stored in an airtight container with plastic wrap pressed against the surface of the buttercream in the fridge for up to 5 days or frozen for up to 3 months - re-whip before using.

COCOA ONLY METHOD

1. In the bowl of a stand mixer using the whisk attachment, beat the butter, heavy cream, golden syrup, salt, and vanilla together on medium to high speed until light and fluffy and significantly increased in volume and lightened in colour. 
2. Add the powdered sugar and cocoa powder and mix on low to incorporate, then increase the speed of the mixer to combine fully. Add the melted chocolate, and mix again to incorporate. 
3. If your buttercream consistency is not to your liking (you want it a little softer and fluffier), you can add warm cream 1 Tbsp at a time, beating well after each addition and adjusting if necessary until the desired consistency is reached. I find that I do not usually need to add extra cream. 
4. Switch to the paddle attachment and mix on low speed for about 5 minutes to remove any large air bubbles. 
5. Use immediately - this is a crusting buttercream so it will set. Leftovers can be stored in an airtight container with plastic wrap pressed against the surface of the buttercream in the fridge for up to 5 days or frozen for up to 3 months - re-whip before using.