1. Preheat the oven to 350°F and place a rack in the middle of the oven. Spray a 9-inch cake pan with baking spray.
2. Sift the cake flour and baking soda into a large bowl. Add the sugar and ½ teaspoon of the salt and whisk to combine.
3. To a medium saucepan, add the butter, oil, cocoa powder, coffee granules, and water. Cook over medium heat, whisking constantly, until the butter melts and everything comes together, about 3 minutes. Remove from the heat—it’s important that the mixture doesn’t get too hot and start to boil.
4. Pour the cocoa mixture into the flour mixture and stir until just combined. It will be a thick, paste-like batter, similar to box brownie mix. Touch the batter to make sure it isn’t hot (warm is okay). Stir in the buttermilk and then whisk in the egg, egg yolk, and vanilla just until combined. The batter will be loose and a little liquidy. It’s important that you don’t overmix it.
5. Pour the batter into the prepared cake pan and bake until a cake tester or toothpick comes out clean and the center is set and slightly domed, about 30 minutes. Remove from the oven and let cool on a wire rack in the pan for 10 minutes. Remove from the pan and allow to cool completely.
6. Heat the caramel in a medium heat-safe bowl in the microwave until it’s a pourable consistency, about 30 seconds. Stir in the remaining ½ teaspoon salt. Pour the caramel over the cake, allowing it to drip down the sides. Slice and serve.

FOR THE CREAMY CARAMEL

1. Add the sugar, corn syrup, and water to a saucepan, taking care not to get any sugar on the sides of the pot. Use your index finger to swish the sugar around just enough so it is moistened with
   water. If you spot any sugar crystals on the side of the pot, use a wet pastry brush or towel to
   wipe them away. (Any stray sugar crystals on the side of the pot could start a chain reaction,
   causing the entire mixture to crystallize instead of caramelize.)
2. Set the saucepan over medium-high heat. Do not stir or otherwise agitate it. Let it cook until all
   the sugar dissolves and the liquid begins to bubble, at first rapidly and then slowing down, with
   the bubbles taking their time before they pop. Eventually, the liquid will start to turn a pale
   yellow, then a darker yellow, about 10 minutes.
3. Once the color starts to turn, it’s important to keep a very close eye on the mixture. It will transform from a pale caramel to deep caramel in just seconds, once it gets going. Continuing to cook the sugar, at around 11 minutes, begin to check the color continually by spooning a little onto a white plate. It reaches the correct color at about 11 minutes 30 seconds. (This is the
   color of caramel chews that the hat-wearing, cane-wielding ladies at church would give us after
   Sunday school.)
4. Have the cream and a whisk or fork nearby. When the sugar mixture is the color of caramel immediately pour the cream into the caramel a little at a time while whisking. It will sputter and
   create a lot of steam. Be careful not to burn yourself. (Use an oven mitt to protect the hand doing the whisking.)
5. Continue to whisk until the caramel is completely smooth, 1 to 1 ½ minutes. It may continue to
   bubble, and that’s fine.
6. Remove the saucepan from the heat and stir in the butter until it’s completely incorporated. Stir in
   the salt, if using. Cool at room temperature, then transfer to an airtight container.