Place 3 cups of the milk with the butter and sugar in a pot and bring to a boil, cook over low heat for about 5 minutes, stirring occasionally.
Place the rest of the milk, butter, egg yolks, and crackers in a blender and blend until well combined.
Add the egg yolk mixture slowly to the milk and stir well. Continue over low heat and simmer, until slightly thickened, about 5 minutes. Remove from the heat and serve warm. Sprinkle with ground cinnamon.