Preheat oven to 350°F (175°C). Grease and line a 9x13 inch pan with parchment.

In a large mixing bowl, whisk together flour, cocoa powder, salt, baking powder, and baking soda.

In another bowl, whisk together the eggs, vanilla, melted butter, sugar, and sour cream until smooth and fully combined.

Add the wet ingredients to the dry and stir to mix lightly. Some remaining unmixed flour is ok at this point.

Slowly whisk in the hot coffee, mixing until the batter is smooth and glossy. It will be pourable.

Pour into prepared pan and bake for 30–33 minutes, or until a toothpick inserted in the center comes out clean.

Let the cake cool completely in the pan.

Place chopped chocolate in a heatproof bowl.

Heat heavy cream in a saucepan over medium heat until just simmering.

Pour hot cream/butter over chocolate and cocoa. Let sit 3–4 minutes.

Stir until completely melted and smooth. Add cocoa powder, vanilla extract and a pinch of salt.

Add room temperature butter and whisk until fully incorporated.

Let the ganache sit at room temperature for 30–40 minutes, stirring occasionally, until it thickens to a spreadable texture.

Spread frosting evenly over the cooled cake.