Mix together sugar, flour, cocoa powder, baking soda, and salt. Add the eggs, buttermilk, oil, and vanilla.
Add in boiling water of hot coffee. Pour into a cake pan and bake.
Separately, mix together sugar, flour, cornstarch, salt, and cocoa powder. Whisk in milk and simmer until thickened.
Pour into a bowl and chill. Separately, melt chocolate. Beat butter and vanilla in a stand mixer.
Add the cooled chocolate mixture and mix until smooth. Beat in the melted chocolate.
Frost the cooled cake with the frosting and serve. Enjoy this best ever chocolate cake!
Watch our full step by step instructional video to learn how to make the best Chocolate Cake.
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