Make the cake: Set a rack in the center of the oven and heat to 350 degrees. Generously butter two 9-inch baking pans and line the bottoms with parchment paper.

In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl, combine the granulated sugar, flour, cocoa powder, baking powder, baking soda and salt. Whisk until well combined and no lumps remain.

In a medium bowl, whisk the melted butter with the sour cream, oil, eggs and vanilla.

Add the sour cream mixture to the dry ingredients. Mix on low until the dry ingredients are moistened, then turn the mixer to medium-high and mix for 2 minutes, scraping the bottom and sides of the bowl halfway through. Carefully fold the coffee into the batter using a flexible spatula.

Divide the batter evenly between the prepared pans and tap them on the counter a few times to release any large air bubbles. Bake until puffed and a toothpick inserted into the center comes out clean, 35 to 40 minutes.

Set the pans on a wire rack and let the cakes cool for about 20 minutes. Run a thin knife around the edges of the pan and carefully turn the cakes out onto the rack to cool completely. (You may have to tap the pans gently on the rack to release each cake.)

While the cakes bake, make the Irish cream frosting: Clean the stand mixer bowl and paddle. Add the softened butter to the mixer bowl and mix on medium-high until smooth, stopping the mixer occasionally to scrape the bottom and sides of the bowl. Add the powdered sugar, Irish cream and salt. Mix on low until the sugar is moistened, then turn the speed up to medium-high and whip until smooth and fluffy, about 5 minutes. Scrape the bowl occasionally to ensure that the frosting is evenly mixed. Taste and add a bit more salt if desired. (The frosting can be kept at room temperature while the cake finishes baking and cooling.)

When the cakes are nearly cool, make the chocolate ganache: Bring the heavy cream to a simmer in a small saucepan set over medium heat. To a heat-safe bowl, add the chocolate, vanilla extract and salt. Pour the hot cream into the bowl with the chocolate and let sit for 2 minutes. Add the Irish cream, then whisk the mixture until smooth. Refrigerate for about 30 minutes, whisking occasionally, until the ganache has a thick, fudgy, spreadable texture.

Assemble the cake: Just before frosting the cake, stir the Irish cream frosting vigorously with a flexible spatula to knock out any large air bubbles. (This will help to make the final frosting smooth.) Trim the cakes so the tops are flat, if needed. Place one layer of cake, trimmed-side up, on a serving platter. Spread the ganache over the top of the cake. Place the second cake layer on top of the ganache, trimmed-side down, and press gently. Spread a thin layer of frosting over the top and sides of the cake, and be careful not to transfer crumbs back to the bowl of frosting. Refrigerate the cake until the frosting is firm, about 30 minutes.

Spread the remaining frosting over the top and sides of the chilled cake. Serve the cake at room temperature, using a hot, clean and dry knife for the tidiest slices. (Store any leftover cake, covered, at room temperature for up to 4 days.)