1. Preheat the oven to 350 F and line 2 cupcake trays with muffin liners. You will be making 18 cupcakes in total. In a large mixing bowl, sift together the flour, cocoa powder, baking soda, baking powder and salt. Set aside.
2. In the bowl of a stand mixer fitted with the paddle attachment, or using a handheld mixer, beat the butter and sugars together on high until soft and fluffy, about 1-2 minutes. Add the oil, then the eggs, one at time. Add in the sour cream and mix until combined, then add the melted chocolate and extracts and beat until smooth.
3. With the mixer running on low, add half of the dry ingredients to the mixture, followed by half of the boiling water. Repeat with remaining dry ingredients and remaining boiling water, only mixing until just combined.
4. Fill the liners 2/3 full and bake in the oven for 20 minutes. Do not open the oven door until 18 minutes has passed. Check the cupcakes with a toothpick to ensure it comes out clean. Remove the cupcakes from the oven and allow them to completely cool before frosting.
5. Prepare the mint buttercream. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on high for 1 minute before adding the powdered sugar and mint extract, and beating on high again. Add the heavy cream, starting with 1 tbsp and adding more to ensure the right consistency. Add the food coloring, if using, and beat until combined. Pipe or spread the frosting onto the cooled cupcakes and serve!

Frosted cupcakes will last at room temperature, in an airtight container, for 2-3 days. Frosted or unfrosted cupcakes can be stored in the freezer for up to 2 months, thawing overnight in the fridge.