Using a saucepan on low heat, cook butter, cocoa, a pinch of cinnamon if desired, until blended. Add milk or cream and bring to a boil. Remove from heat.
Add powdered sugar, vanilla, and pecans, and mix to combine.
Once the cake has been cooled and iced, garnish with additional pecans if desired. Cut into squares and enjoy!
Make sure to spread the icing as soon as you make it. It sets up quickly.
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