In a glass bowl, break up your chocolate and cube your butter. Place over a pan of hot water, ensuring the bowl does not touch the water. Cover your choc and butter with a plate and stir every 30 seconds or so till 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 your yummy chocolate ganache!