Preheat the oven to 350 degrees Fahrenheit. Spray your bundt pans with cooking spray. Sprinkle a little bit of cocoa powder and tap them to coat the inside of the pans.
In a medium mixing bowl, whisk together the flour, cocoa powder, salt, baking soda and baking powder. Set aside for a second.
In the bowl to your stand mixer, use the whisk attachment to beat together the buttermilk, coffee, eggs, vegetable oil and granulated sugar on medium-high speed until fully combined.
Slowly add the flour mixture, approximately 1/2 cup at a time, and beat on medium until combined. Beat for an additional 2 minutes after it comes together. The batter is very thin.
Pour the batter into your prepared bundt pans. Fill each one approximately 75% full. Place the bundt pans on a baking sheet and bake for 18-20 minutes or until the cake appears dry and an inserted toothpick comes out clean.
Cool in the pans for 10 minutes before flipping them out on the a cooling rack to cool completely.
Once the cakes have cooled, we can start on the frosting. In the bowl to your stand mixer, beat the softened butter until smooth.
Add 2 cups of the powdered sugar to the bowl with the pumpkin pie spice. Start beating on low and increase the speed to high as the sugar mixes in.
Add another cup of powdered sugar and 2 tablespoons of heavy cream. If the frosting is too dry, add another tablespoon of heavy cream and beat until smooth.
Add 1 teaspoon of the orange food colouring and beat in. Add more if needed to get a vibrant orange colour.
Form the modelling chocolate or the fondant into a stem shape. You’ll want the base the stem to be diameter of the centre portion of your bundt pan.
Now it is time to assemble your cakes. Spread the orange frosting onto the bottom of one of the cooled bundt cakes, evenly, about a 1/4 of an inch thick. Top with a second bundt cake so that the bottoms are pressed together and the shape resembles a mini pumpkin.
Ice the entire outside of the cake with the orange frosting, use a knife or a flexible cake scraper to give you the indents that you find in a pumpkin. The shape of your bundt pans will help with this.
Top with your chocolate or fondant stem and serve immediately.