Melt the chocolate in a double boiler or in the microwave. Wash the strawberries and pat dry with kitchen paper. Dip the strawberries into the white chocolate and arrange on a baking tray lined with foil.
To the remainder of the chocolate, add the cocoa powder and mix in. Using a spoon, drizzle the milk chocolate across the strawberries.
Transfer to the fridge to set. Chill for 2 hours prior to serving.
If you'd rather user milk or dark chocolate instead of adding cocoa powder to the white chocolate, that works great too. You should only need a couple of tablespoons of the melted chocolate for the drizzle.