Preheat oven to 375 degrees F and line muffin tins with cupcake liners.
In a large bowl, mix flour, cocoa, baking powder, baking soda, and salt together. In a small bowl combine buttermilk, pumpkin and vanilla.
In the bowl of a standing mixer, cream butter and sugars until light and fluffy. Beat in eggs one at a time. While mixing on low, alternately add dry ingredients and pumpkin mixture in thirds. When evenly combined, pour into muffin tins and bake for 15-18 minutes or until toothpick comes out clean.
When cool enough to handle, remove cupcakes onto wire rack to cool completely.
For the Frosting:
Beat whipping cream and 3/4 cup powdered sugar with an electric mixer until soft peaks form. Add food coloring and mix until stiff peaks.
In another bowl, beat cream cheese on medium-high until light and fluffy. Mix in remaining 2 cups powdered sugar, cinnamon, and vanilla until combined. Fold in the whipped cream until well mixed. Place frosting in piping bag fitted with a large round tip. Pipe a dollop of frosting in the middle for height and then pipe the frosting around and spiral up. Release pressure and then lift when you reach the top. Place in the fridge for at least 30 minutes before adding glaze.
For the glaze:
Place chocolate, butter, and corn syrup in a heatproof bowl. Boil whipping cream on the stove or in the microwave (careful it doesn't boil over) and pour it over the chocolate and let it sit for 3 minutes. Mix with a whisk until smooth and let it sit for 3-5 minute to allow it to thicken a little. Spoon the glaze on top of each cupcake pushing it off the edges to drip down the frosting. Refrigerate until ready to serve.