1. Prepare the Pan and Oven:

Preheat the oven to 350°F (175°C).

Spray a 9-inch round cake pan with nonstick baking spray.

Line the bottom of the pan with parchment paper.

Spray the parchment paper with nonstick baking spray. Set the pan aside.

2. Combine Dry Ingredients (Cake): Sift the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking soda, baking powder, and salt into a large bowl.

Whisk to combine.

3. Combine Wet Ingredients (Cake):

In a separate large bowl, whisk together the buttermilk, canola oil, egg, and vanilla extract.

4. Combine Wet and Dry Ingredients:

Gradually add the flour mixture to the buttermilk mixture.

Whisk until well combined.

5. Add Coffee: Add the freshly brewed strong coffee to the batter.

Whisk just until evenly incorporated.

6. Bake the Cake:

Transfer the batter to the prepared pan.

Bake for 28 to 32 minutes, or until a toothpick inserted into the center of the cake comes out clean.

7. Cool the Cake:

Let the cake cool in the pan for 15 minutes.

Then, invert the cake onto a cooling rack to cool completely, about 1 hour.

8. Make the Chocolate Ganache:

While the cake is cooling, make the chocolate ganache.

In a 4-cup heat-proof liquid measuring cup with a spout (or another heatproof bowl), combine the bittersweet chocolate chips and 1 tablespoon of salted butter.

In a small saucepan, bring the heavy cream and light corn syrup to a low simmer over medium-low heat.

Pour the warm cream mixture over the chocolate mixture.

Let it stand for 2 minutes to soften the chocolate.

Stir until very smooth.

Set aside until cooled slightly, but still pourable (about 105°F/40°C), 2 to 5 minutes.

9. Prepare for Ganache Application: While the chocolate ganache is cooling, set the completely cooled cake, still on the wire rack, inside a rimmed baking sheet. This will catch any ganache that drips off.

10. Pour Ganache Over Cake:

Once the ganache has cooled slightly, pour it over the cake.

Making sure to completely cover the top and sides. Let any excess ganache run off into the rimmed baking sheet.

Smooth the top of the cake using a large offset spatula.

11. Chill (and Make Peanut Butter Swirl – Optional):

Immediately transfer the cake to the refrigerator to harden the ganache, about 30 minutes.

(Optional) For the peanut butter ganache swirl: While the chocolate ganache is cooling, combine the peanut butter chips and butter in a small microwavable bowl. Microwave on high until the mixture is melted and smooth, about 30 seconds, stopping to stir after 15 seconds. Transfer the peanut butter mixture to a small Ziploc bag with a ¼-inch hole cut in the corner. Immediately after covering the cake with warm ganache in Step 10, pipe 6 equally spaced lines of the peanut butter mixture across the top of the cake. Using a paring knife or skewer, drag the tip through the peanut butter and ganache in 7 evenly spaced lines perpendicular to the piped peanut butter, alternating the direction of each line. Then proceed with chilling.

12. Serve:

Using 2 large spatulas, carefully transfer the cake to a serving platter.

Serve slightly chilled or at room temperature. Enjoy!