In a glass bowl, break up your chocolate and cube your butter. Place over a saucepan of hot water, ensuring the bowl does not touch the water. Cover your chocolate and butter with a plate then stir every 30 seconds or so until melted.
When your butter and chocolate are melted and smooth, take off the heat and stir the cinnamon in until fully combined.
Cover bowl with foil and put in fridge for about 2 hours until set. Keep stirring every so often.
Now you can take it out of fridge and use to cover your cakes, pancakes, or just eat.