Add the dates, nut butter, salt and grated zest of half of the orange to a food processor, blending until smooth and starts to become 'fudge' like. It will start to come away from the sides.
Press the mixture into the lined loaf tin or silicone mould. Pop in the freezer for up to an hour.
Melt the chocolate in a heatproof bowl in short bursts of 30 seconds in the microwave. Alternatively, pour boiling water in a pan and rest a bowl over the top (the bowl should not sit in the water). Add the chopped chocolate and keep stirring until it is melted. I like to add a teaspoon of coconut oil to chocolate before I melt it, just to make it more glossy and prevent it seizing, but don't worry if you don't have any, it will still melt fine.
Pour the melted chocolate over the set 'fudge', sprinle over the remaining orange zest and pop back in the fridge to set (about 10 - 15 mins). Cut into squares if you have not used individual moulds.
This fudge needs to be stored in the fridge and will last about 5 days