Line two baking trays with baking parchment. Tip both flours, the oats and the butter into a food processor and blitz until it resembles fine breadcrumbs. Alternatively, rub the butter into the flour mixture using your hands. Stir in the sugar, bicarb and 3/4 tsp salt, then pour in the milk. Bring together into a cohesive dough then flatten into a disc, cover and chill in the fridge for at least 30 minutes.

Lightly flour a clean work surface and tip the biscuit dough out. Roll out until roughly 0.5cm thick, then stamp out biscuits using a 6-7cm cutter. Arrange on the baking trays and chill for a further 30 minutes, or up to 2 hours.

Heat the oven to 200C/180C fan/gas 6. If not covering the biscuits with chocolate, you can make a pattern on the tops with a fork or a skewer, if you like. Bake in the oven for 12-15 mins until golden around the edges. Leave to cool completely on the trays.

To cover the biscuits with chocolate, melt the chocolate in a heatproof bowl, set over a pan of gently simmering water. Line a cooling rack with baking parchment. Once the biscuits have cooled, dip the top of each biscuit into the chocolate, then carefully transfer to the rack to set. Decorate the tops by dragging a toothpick through in wavy lines, if you like.