Preheat oven to 180 degrees C. Grease 24 muffin cups or line with muffin cases.
Mix together the flour, cocoa and bicarbonate of soda; set aside.
Beat the butter and sugar with an electric mixer in a large bowl until light-coloured and fluffy. Add the eggs one at a time allowing each egg to blend into the butter mixture before adding the next. Mix in the vanilla with the last egg.
Pour in the flour mixture alternately with the buttermilk mixing until just incorporated. Fold in the grated courgettes, raspberries and chocolate chips; mixing just enough to evenly combine.
Spoon the batter into the prepared muffin cups, filling each 3/4 full.
Bake in the preheated oven until a toothpick inserted into the centre comes out clean; about 20 minutes. Cool in the tins for 10 minutes before removing to cool completely on a wire rack.