Preheat the oven to 180°C (gas 4) and line a baking tray with baking paper.
Place the flour, stevia, cacao powder, butter and milk in a food processor bowl and process to make a firm dough. Transfer the dough to a lightly floured work surface and knead until smooth. Roll the dough out between two sheet of baking paper to make a rectangle (about 5 mm thick). Cut into 16 smaller rectangles. Transfer to baking tray and bake in the oven for 10 minutes.
Meanwhile, to make the ganache, place all the ingredients in a small bowl and beat until fluffy. (For a firmer frosting set the ganache mixture in the fridge for 15 minutes)
Remove the biscuits from the oven and allow to cool. Once cooled, spread a thin layer of ganache over eight of the biscuits and top each one with another biscuit, sandwiching them together. Place in the fridge while you make the chocolate coating.
Melt the chocolate slowly in a microwave (or in a heatproof bowl over a saucepan of boiling water, making sure the base of the bowl does touch the water). Dip each biscuit sandwich in the melted chocolate and place on the baking paper. Return to the fridge to set before serving. Store in a sealed container in the fridge for up to 1 week or in the freezer for up to 3 months.
From Wilson, Sarah. “I Quit Sugar: Simplicious.” I Quit Sugar: Simplicious, Macmillan, 2016, p. 274.