Preheat the oven to 190°C, fan 170°C, gas mark 5. In a large bowl, cream the butter and sugar together with the back of a wooden spoon, for 2 minutes until light and fluffy. Break in the egg, strawberries and raspberries (see cook's tip tip below), and beat until combined.
Sift the plain flour and bicarbonate of soda into a separate mixing bowl and mix in the salt and chocolate, then stir into the butter mixture until combined totally. Spoon equal portions of the mixture (about a heaped dessertspoon) onto two greased baking trays, allowing space for the biscuits to spread whilst cooking.
Bake for 15-20 minutes until lightly golden, swapping the trays over in the oven if they are on different shelves. Allow to cool for 5 minutes, then transfer to a cooling rack.
Cook's tip: After washing the strawberries and raspberries, make sure they are dry, before you chop and add to the mixture, by dabbing them with kitchen roll.
*All information included in this recipe has been provided by Angus Soft Fruits.