### Instructions
**Part 1: The Fudgy Chocolate Cake**
1. **Prep Work:** Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan. You can also line it with parchment paper, leaving an overhang on the sides for easier lifting.
2. **Combine Dry Ingredients:** In a large bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt.
3. **Combine Wet Ingredients:** In a separate medium bowl, whisk together the buttermilk, vegetable oil, eggs, and vanilla extract until well combined.
4. **Combine Wet and Dry:** Pour the wet ingredients into the dry ingredients and mix on low speed with an electric mixer until just combined. Do not overmix.
5. **Add Hot Coffee:** Carefully pour in the hot coffee and mix on low speed until the batter is smooth. The batter will be thin, don’t worry!
6. **Pour Batter:** Pour about two-thirds of the chocolate cake batter into the prepared baking pan, spreading it evenly. Reserve the remaining one-third of the batter for later.
**Part 2: The Gooey Cream Cheese Filling**
1. **Cream Cheese Mixture:** In a medium bowl, beat the softened cream cheese and granulated sugar with an electric mixer until smooth and creamy.
2. **Add Remaining Ingredients:** Beat in the egg, vanilla extract, and pinch of salt until well combined.
3. **Spread Filling:** Carefully spoon the cream cheese filling over the chocolate cake batter in the pan, spreading it gently to cover the cake layer.
4. **Sprinkle Chocolate Chips:** Evenly sprinkle the chocolate chips over the cream cheese filling.
5. **Add Remaining Batter:** Gently dollop the reserved one-third of the chocolate cake batter over the cream cheese filling. Don’t worry if it doesn’t completely cover the filling; it will spread as it bakes.
**Part 3: Baking and Cooling**
1. **Bake:** Bake for 40-50 minutes, or until a wooden skewer inserted into the chocolate cake (avoiding the cream cheese center) comes out with moist crumbs, but not wet batter. The cream cheese filling will be set but still wobbly in the center.
2. **Cool:** Let the cake cool completely in the pan on a wire rack before attempting to slice or frost. This is crucial for the filling to set properly.
**Part 4: Chocolate Ganache (Optional)**
1. **Heat Cream:** In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer around the edges. Do not boil.
2. **Melt Chocolate:** Remove from heat and immediately pour the hot cream over the finely chopped dark chocolate in a heatproof bowl. Let sit for 5 minutes without stirring.
3. **Whisk Ganache:** After 5 minutes, whisk gently from the center outwards until the chocolate is completely melted and the ganache is smooth and glossy.
4. **Pour Over Cake:** Once the cake is completely cooled, pour the ganache over the top and spread evenly. Allow the ganache to set slightly before serving.
### Short Tips
* **Don’t overmix the cake batter!** Overmixing develops gluten, which can lead to a tough cake. Mix until just combined.
* **The hot coffee is key!** It not only enhances the chocolate flavor but also contributes to the cake’s incredible moistness.
* **Ensure your cream cheese is softened.** This prevents lumps in your filling.
* **Cool completely!** Patience is a virtue here. Rushing the cooling process will result in a messy, unset filling.
* **For an extra decadent touch,** a sprinkle of flaky sea salt on top of the ganache amplifies the chocolate flavor beautifully.
