Spiced chocolate molasses buttons

Method

1. For the dough, sift together the flour, cocoa powder, cinnamon, ginger, allspice, bicarbonate of soda and sea salt into a mixing bowl.
2. Put the 140g butter in another large bowl with the muscovado sugar and vanilla extract. Beat with an electric mixer on a medium-high speed for about 4 minutes or until the mixture is noticeably paler, transforming from a dark, gritty-looking mixture to something fluffier and latte-like in colour. Beat in the egg until completely absorbed. Beat in the molasses until blended.
3. Reduce the mixer speed to low, then gradually mix in the bowlful of dry ingredients. Mix until blended and even in colour. Cover the bowl with cling film and chill the dough for about 2 hours.
4. When you’re ready to bake, position 2 racks in the upper and lower thirds of the oven and heat to 180°C/160°C fan/gas 4. Line 2 baking sheets with baking paper.
5. Pour the demerara sugar onto a plate. Using a small ice cream scoop with a capacity of about a tablespoon, portion the dough into balls. Roll the dough balls in the demerara sugar, coating each one completely. Put 12 of the sugar- coated balls on each prepared baking sheet, evenly spacing them.
6. Bake the cookies for 10 minutes or until they are set at the edges but still very soft in the centre. Quickly pull the baking sheets from the oven to retain the heat then, using the handle of a wooden spoon, make a deep, fairly wide indentation in the centre of each cookie. Return to the oven for 5 minutes more. Remove, then cool on the baking sheets set on wire racks. If the indentations have become shallow, press them down again while the cookies are warm.
7. To make the filling, put the chocolate and butter in a heatproof bowl. Melt in the microwave in 30 second bursts, stirring well after each interval (or melt in a glass bowl over a pan of barely simmering water). Stir in the molasses. Transfer the ganache to a small zip-lock bag or disposable piping bag and work it toward the corner. Snip off a tiny bit at the corner, then use to fill the indent of each cooled cookie with ganache. Leave to set at room temperature for about 1 hour or until the ganache is firm.