1. Bake the Chocolate Cake

1. Preheat your oven to 400°F. Grease a half-sheet pan with cooking spray and line it with parchment paper.
2. In a mixing bowl, sift together flour and sugar. Set aside.
3. In a saucepan, combine oil, butter, water, and cocoa powder. Heat until it just begins to boil, then pour over the dry ingredients and mix until smooth. Add buttermilk, baking soda, salt, vanilla extract, and eggs; stir until fully combined.
4. Pour the batter into the prepared pan and bake for 15–18 minutes or until a toothpick inserted in the center comes out clean. Let cool completely before cutting into three pieces (~4″x8″). Freeze the pieces until firm.

2. Make Coffee Ice Cream

1. In a saucepan over medium heat, combine half-and-half, heavy cream (1½ cups), sugar, espresso powder, and salt. Stir until sugar dissolves.
2. In a separate bowl, whisk egg yolks with the remaining heavy cream. Slowly temper the yolks by adding hot cream mixture while whisking constantly to prevent curdling. Return everything to the saucepan and cook over medium-low heat until slightly thickened (it should coat the back of a spoon). Do not boil.
3. Strain through a fine-mesh sieve into a bowl and stir in vanilla extract. Cover with plastic wrap touching the surface and refrigerate until chilled. Once cold, churn in an ice cream maker (~45 minutes). Freeze until firm but spreadable (~1–2 hours).

3. Assemble the Cake

1. Line a loaf pan (4″x8″) with plastic wrap for easy removal later. Place one layer of frozen cake at the bottom of the pan, spread coffee ice cream evenly (~¾–1 inch thick), cover with plastic wrap, and freeze until firm (~1 hour).
2. Add another layer of cake and ice cream, repeating the process before topping with the final piece of cake. Freeze until completely firm.

4. Prepare Ganache & Finish

1. Heat heavy cream in a saucepan until hot but not boiling; pour over chocolate morsels in a heatproof bowl. Let sit for one minute before stirring until smooth and glossy. Cool ganache until thickened but still pourable (~1 hour).
2. Place your assembled cake on a cooling rack set over a sheet pan. Pour ganache evenly over the top, letting it drip down naturally to coat all sides. Freeze briefly to set ganache.