PREPARE CAKE:
- Heat oven to 350 degrees. Grease and flour a 18×12 rimmed baking sheet (also known as a half sheet pan). For a thicker cake, you can use a 9×12 metal or glass casserole pan, increasing the cooking time by approximately 10 minutes.
- In large saucepan, over medium heat, bring sugar, butter, cocoa, and water to a boil, whisking constantly. Once it begins to boil, remove from heat.
- In a separate large mixing bowl, with a stand or hand mixer, place sifted flour and salt in the bowl. Add the chocolate mixture, beating at medium low speed to incorporate the flour into the chocolate. Add the sour cream, eggs, and vanilla extract, beating just until thoroughly combined.
- Pour batter into prepared pan.
- Bake at 350 degrees for approximately 25 minutes. If using a 9×12 pan, increase cooking time by 10 minutes. Let cool on wire rack while you make the icing.
PREPARE ESPRESSO FUDGE ICING:
- Whisk together cocoa, butter, and milk in a small saucepan. Bring to a simmer, then remove from heat.
- Stir in the vanilla extract and espresso powder.
- With a hand mixer, beat in the confectioner’s sugar until smooth.
- Add additional cream or confectioner’s sugar if needed for desired consistency.
- To assemble cake, pour icing over the top of the warm cake. Garnish with walnuts or pecans, if desired.
