Spray a 9 x 13 inch pan with cooking spray and then line bottom with parchment paper leaving an overhang on 2 sides. If you are planning on serving the cake from the pan, you can skip the parchment paper. Grease the pan with butter and then coat with cocoa powder, tapping out any excess.

Preheat the oven to 350 degrees Farenheight.

Combine milk, sour cream, oil, eggs and vanilla in another bowl.

Slowly add the wet ingredients into the dry until just combined with a few streaks of flour still remaining. Carefully add the hot coffee (or hot water) and gently stir to combine.

Place sugar in a large saucepan over medium heat. Once the sugar starts to dissolve, stir until it dissolves completely, 10-15 minutes.

Once sugar has dissolved, stop stirring and cook over medium heat until the sugar turns a deep amber color, about 1-3 minutes. Don’t walk away during this step! It can burn very quickly if you aren’t paying attention.

Immediately add the cubed butter and whisk constantly until the butter is melted. It will bubble up a lot.

Remove the pan from the heat and slowly pour in the heavy cream while whisking constantly. Be careful as it will bubble up again. Continue whisking until the caramel is smooth.

If clumps of sugar remain, place the pan back over medium heat for a couple minutes to melt completely.

Add the salt and whisk until combined. Let the caramel cool completely before adding to the frosting.

Using a stand mixer or mixing bowl and hand mixer, combine room temperature butter with powdered sugar.

Mix at low speed for about 2 minutes until combined. Add the vanilla and mix well.

Mix at medium speed for 2 minutes until light and fluffy.

Add the cooled salted caramel and beat until incorporated.