Chocolate Bourbons

Dough

• 110 g unsalted butter, diced
• 110 g light brown sugar
• 30 g golden syrup
• 170 g self-raising flour
• 60 g cocoa powder
• 60 g cornflour
• 30 g water, plus 1 Tbsp
• 1 pinch fine sea salt

Filling

• 75 g unsalted butter, soft
• 150 g icing sugar
• 30 g cocoa powder
• ½ tsp vanilla extract
• 3 tsp water, boiling