Preheat your oven to 425°F and line 8 muffin wells with large paper muffin liners, or if making standard size muffins, place one liner in each well. Spray lightly with nonstick spray. Melt your butter and add your oil to it to cool it down.
In a large mixing bowl, whisk together all-purpose flour, cocoa powder, sugar, baking powder, baking soda, and kosher salt.
In a measuring cup, or medium bowl, whisk together buttermilk, eggs, vanilla, and 3 tablespoons of hot espresso.
Pour wet ingredients into dry ingredients and mix halfway, then begin drizzling in melted butter and oil while continuing to mix.
Mix in your choice of chocolate. I used chopped semi-sweet chocolate, milk chocolate chips, and mini chocolate chips. Reserve some for the tops of the muffins.
Place one scoop of batter into the muffin wrappers. Press one ball of ganache into the batter. Top with another scoop of batter and sprinkle the tops with more chocolate.
Bake at 425°F for 5 minutes, then turn down the oven to 350°F without opening the oven door. Bake for another 15 to 18 minutes, or until muffins are set and a toothpick inserted into the top comes out clean or with just a bit of ganache.
For best results, remove from pan and let cool on a wire rack for at least 30 minutes, or your muffins may fall apart. I’ve never actually made it that long, but you should do as I say, not as I do.