To make donuts: Preheat oven to 350°. Grease pan and set aside.
Sift together flour, cocoa powder, baking soda, baking powder, and salt.
In a separate bowl, mix together sour cream, melted butter, and sugars until combined. Stir in vanilla and one egg at a time.
Gently fold the flour mixture into wet ingredients and mix by hand just until combined.
Fill a piping bag with batter and fill donut pan 2/3 of the way full.
Bake for 12 minutes until a toothpick comes out clean. Remove from oven and let cool for 3-5 minutes, then remove from pan.
To make the ganache: In a small saucepan, bring cream to a boil. Remove from heat and add chocolate. Stir until smooth. Set aside for 15-20 minutes until ganache has cooled and thickened a bit.
To make the buttercream for decoration: In a mixing bowl, mix together butter and sugar, add milk and vanilla. Mix on high for 3 minutes. Put into a piping bag and cut a very small hole at the end. Set aside.
To assemble chocolate reindeer donuts: Dip donuts into the ganache, then place on a cooling rack until ganache sets.
Place eyes, and cranberry in the center as the nose.
Break/cut pretzels in half, length-wise for antlers.